diff --git a/CMake/ITKConfig.cmake.in b/CMake/ITKConfig.cmake.in
index 7a77ae3c07a7..2286442eb030 100644
--- a/CMake/ITKConfig.cmake.in
+++ b/CMake/ITKConfig.cmake.in
@@ -26,9 +26,6 @@ set(ITK_VERSION_MAJOR "@ITK_VERSION_MAJOR@")
 set(ITK_VERSION_MINOR "@ITK_VERSION_MINOR@")
 set(ITK_VERSION_PATCH "@ITK_VERSION_PATCH@")
 
-# If ITK was built with version 4 compatibility features.
-set(ITKV4_COMPATIBILITY "@ITKV4_COMPATIBILITY@")
-
 # Remove all legacy code completely.
 set(ITK_LEGACY_REMOVE "@ITK_LEGACY_REMOVE@")
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1267b1aae95b..77075e99c7d0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -325,20 +325,16 @@ cmake_dependent_option(
   OFF
   "NOT ITK_LEGACY_REMOVE"
   OFF)
-# The disabling of legacy code, and the ITKv4 compatibility option can not both be
-# requested. If removal of legacy code is requested, then ITKV4_COMPATIBILITY must
-# be off.
-cmake_dependent_option(
-  ITKV4_COMPATIBILITY
-  "Enable LEGACY compatibility with ITK4.x when possible."
-  OFF
-  "NOT ITK_LEGACY_REMOVE"
-  OFF)
+
 mark_as_advanced(
   ITK_LEGACY_SILENT
   ITK_LEGACY_REMOVE
   ITK_FUTURE_LEGACY_REMOVE
-  ITKV4_COMPATIBILITY)
+  )
+
+if(ITKV4_COMPATIBILITY)
+  message(FATAL_ERROR "ITKV4_COMPATIBILITY is removed starting in ITK version 4.0, this option is no longer valid.")
+endif()
 
 if(ITKV3_COMPATIBILITY)
   message(FATAL_ERROR "ITKV3_COMPATIBILITY is removed starting in ITK version 5.0, this option is no longer valid.")
diff --git a/Documentation/docs/migration_guides/itk_6_migration_guide.md b/Documentation/docs/migration_guides/itk_6_migration_guide.md
index 369cbe5e7749..6c8f525dc30b 100644
--- a/Documentation/docs/migration_guides/itk_6_migration_guide.md
+++ b/Documentation/docs/migration_guides/itk_6_migration_guide.md
@@ -22,6 +22,10 @@ deprecations and API changes. The new behavior is activated by setting
 `ITK_LEGACY_REMOVE` to `ON`. By default, compatibility with v5 is retained
 (`ITK_LEGACY_REMOVE=OFF`).
 
+Remove support for ITKv4 interfaces
+-----------------------------------
+
+ITKV4_COMPATIBILITY is no longer a supported option.
 
 Require modern C++ language feature use
 ---------------------------------------
diff --git a/Modules/Compatibility/Deprecated/include/itkImageTransformer.hxx b/Modules/Compatibility/Deprecated/include/itkImageTransformer.hxx
index 1c57cee58f29..8e7a0a12866f 100644
--- a/Modules/Compatibility/Deprecated/include/itkImageTransformer.hxx
+++ b/Modules/Compatibility/Deprecated/include/itkImageTransformer.hxx
@@ -323,20 +323,6 @@ ImageTransformer<TInputImage>::ThreaderCallback(void * arg)
   if (threadId < total)
   {
     str->Filter->ThreadedGenerateData(splitRegion, threadId);
-#if defined(ITKV4_COMPATIBILITY)
-    if (str->Filter->GetAbortGenerateData())
-    {
-      std::string    msg;
-      ProcessAborted e(__FILE__, __LINE__);
-      msg += "Object " + std::string(str->Filter->GetNameOfClass()) + ": AbortGenerateData was set!";
-      e.SetDescription(msg);
-      throw e;
-    }
-    else if (str->Filter->GetProgress() == 0.0f) // progress was not set after at least the first chunk finished
-    {
-      str->Filter->UpdateProgress(static_cast<float>(threadId + 1) / total); // this will be the only progress update
-    }
-#endif
   }
   // else
   //   {
diff --git a/Modules/Compatibility/Deprecated/itk-module.cmake b/Modules/Compatibility/Deprecated/itk-module.cmake
index a04eee547b34..c43847844851 100644
--- a/Modules/Compatibility/Deprecated/itk-module.cmake
+++ b/Modules/Compatibility/Deprecated/itk-module.cmake
@@ -2,9 +2,6 @@ set(DOCUMENTATION "This is a collection of classes that are intended to be
 removed from the toolkit.")
 
 set(ITKDeprecatedOnByDefault EXCLUDE_FROM_DEFAULT)
-if(ITKV4_COMPATIBILITY)
-  set(ITKDeprecatedOnByDefault "")
-endif()
 
 itk_module(
   ITKDeprecated
diff --git a/Modules/Core/Common/include/itkImageSource.hxx b/Modules/Core/Common/include/itkImageSource.hxx
index 3103e4256eb5..3602009a7a87 100644
--- a/Modules/Core/Common/include/itkImageSource.hxx
+++ b/Modules/Core/Common/include/itkImageSource.hxx
@@ -45,11 +45,7 @@ ImageSource<TOutputImage>::ImageSource()
   this->ProcessObject::SetNumberOfRequiredOutputs(1);
   this->ProcessObject::SetNthOutput(0, output.GetPointer());
 
-#if defined(ITKV4_COMPATIBILITY)
-  m_DynamicMultiThreading = false;
-#else
   m_DynamicMultiThreading = true;
-#endif
 
   // Set the default behavior of an image source to NOT release its
   // output bulk data prior to GenerateData() in case that bulk data
@@ -287,21 +283,6 @@ ImageSource<TOutputImage>::ThreaderCallback(void * arg)
   if (workUnitID < total)
   {
     str->Filter->ThreadedGenerateData(splitRegion, workUnitID);
-#if defined(ITKV4_COMPATIBILITY)
-    if (str->Filter->GetAbortGenerateData())
-    {
-      std::string    msg;
-      ProcessAborted e(__FILE__, __LINE__);
-      msg += "Object " + std::string(str->Filter->GetNameOfClass()) + ": AbortGenerateData was set!";
-      e.SetDescription(msg);
-      throw e;
-    }
-    else if (!str->Filter->GetDynamicMultiThreading() // progress reporting is not done in MultiThreaders
-             && str->Filter->GetProgress() == 0.0f) // and progress was not set after at least the first chunk finished
-    {
-      str->Filter->UpdateProgress(static_cast<float>(workUnitID + 1) / total); // this will be the only progress update
-    }
-#endif
   }
   // else don't use this thread. Threads were not split conveniently.
   return ITK_THREAD_RETURN_DEFAULT_VALUE;
diff --git a/Modules/Core/Common/include/itkMacro.h b/Modules/Core/Common/include/itkMacro.h
index da4ab71f0846..3370801f59ba 100644
--- a/Modules/Core/Common/include/itkMacro.h
+++ b/Modules/Core/Common/include/itkMacro.h
@@ -1359,11 +1359,7 @@ compilers.
  * classes can be achieved with defining ITKV4_COMPATIBILITY. Code
  * should be migrated to no longer rely on the old virtual interface.
  */
-#if defined(ITKV4_COMPATIBILITY)
-#  define ITK_ITERATOR_VIRTUAL virtual
-#  define ITK_ITERATOR_OVERRIDE override
-#  define ITK_ITERATOR_FINAL
-#elif !defined(ITK_LEGACY_REMOVE)
+#if !defined(ITK_LEGACY_REMOVE)
 #  define ITK_ITERATOR_VIRTUAL virtual
 #  define ITK_ITERATOR_OVERRIDE override
 #  define ITK_ITERATOR_FINAL final
diff --git a/Modules/Core/Common/include/itkProcessObject.h b/Modules/Core/Common/include/itkProcessObject.h
index 509fc314a7b1..068767a06d61 100644
--- a/Modules/Core/Common/include/itkProcessObject.h
+++ b/Modules/Core/Common/include/itkProcessObject.h
@@ -494,12 +494,6 @@ class ITKCommon_EXPORT ProcessObject : public Object
   itkSetClampMacro(NumberOfWorkUnits, ThreadIdType, 1, ITK_MAX_THREADS);
   itkGetConstReferenceMacro(NumberOfWorkUnits, ThreadIdType);
 
-#if !defined(ITK_LEGACY_REMOVE) || defined(ITKV4_COMPATIBILITY)
-  itkLegacyMacro(void SetNumberOfThreads(ThreadIdType count)) { this->SetNumberOfWorkUnits(count); }
-
-  itkLegacyMacro(ThreadIdType GetNumberOfThreads() const) { return this->GetNumberOfWorkUnits(); }
-#endif // !ITK_LEGACY_REMOVE
-
   /** Return the multithreader used by this class. */
   MultiThreaderType *
   GetMultiThreader() const
diff --git a/Modules/Core/Common/src/itkConfigure.h.in b/Modules/Core/Common/src/itkConfigure.h.in
index a427cddb588a..025d8a640888 100644
--- a/Modules/Core/Common/src/itkConfigure.h.in
+++ b/Modules/Core/Common/src/itkConfigure.h.in
@@ -71,7 +71,6 @@
 #endif
 #cmakedefine ITK_DYNAMIC_LOADING
 
-#cmakedefine ITKV4_COMPATIBILITY
 #cmakedefine ITK_LEGACY_REMOVE
 #cmakedefine ITK_LEGACY_SILENT
 #cmakedefine ITK_FUTURE_LEGACY_REMOVE
diff --git a/Modules/Core/Common/src/itkPoolMultiThreader.cxx b/Modules/Core/Common/src/itkPoolMultiThreader.cxx
index 5e829449859d..1673f1bd73f1 100644
--- a/Modules/Core/Common/src/itkPoolMultiThreader.cxx
+++ b/Modules/Core/Common/src/itkPoolMultiThreader.cxx
@@ -86,12 +86,6 @@ PoolMultiThreader::PoolMultiThreader()
   }
 
   ThreadIdType defaultThreads = std::max(1u, GetGlobalDefaultNumberOfThreads());
-#if !defined(ITKV4_COMPATIBILITY)
-  if (defaultThreads > 1) // one work unit for only one thread
-  {
-    defaultThreads *= 4;
-  }
-#endif
   m_NumberOfWorkUnits = std::min<ThreadIdType>(ITK_MAX_THREADS, defaultThreads);
   m_MaximumNumberOfThreads = m_ThreadPool->GetMaximumNumberOfThreads();
 }
diff --git a/Modules/Core/Common/src/itkTBBMultiThreader.cxx b/Modules/Core/Common/src/itkTBBMultiThreader.cxx
index 8fa18d81a562..7c49cac55e48 100644
--- a/Modules/Core/Common/src/itkTBBMultiThreader.cxx
+++ b/Modules/Core/Common/src/itkTBBMultiThreader.cxx
@@ -47,14 +47,10 @@ namespace itk
 TBBMultiThreader::TBBMultiThreader()
 {
   ThreadIdType defaultThreads = std::max(1u, GetGlobalDefaultNumberOfThreads());
-#if defined(ITKV4_COMPATIBILITY)
-  m_NumberOfWorkUnits = defaultThreads;
-#else
   if (defaultThreads > 1) // one work unit for only one thread
   {
     m_NumberOfWorkUnits = 16 * defaultThreads;
   }
-#endif
 }
 
 TBBMultiThreader::~TBBMultiThreader() = default;
diff --git a/Modules/Core/ImageFunction/include/itkInterpolateImageFunction.h b/Modules/Core/ImageFunction/include/itkInterpolateImageFunction.h
index 9bd40c4f22fa..be5cf071663f 100644
--- a/Modules/Core/ImageFunction/include/itkInterpolateImageFunction.h
+++ b/Modules/Core/ImageFunction/include/itkInterpolateImageFunction.h
@@ -127,28 +127,13 @@ class ITK_TEMPLATE_EXPORT InterpolateImageFunction
     return (static_cast<RealType>(this->GetInputImage()->GetPixel(index)));
   }
 
-/** Get the radius required for interpolation.
- *
- * This defines the number of surrounding pixels required to interpolate at
- * a given point.
- */
-#if defined(ITKV4_COMPATIBILITY)
-  virtual SizeType
-  GetRadius() const
-  {
-    // if ITKv4 compatibility is enabled then set the radius to the
-    // largest by default.
-    const InputImageType * input = this->GetInputImage();
-    if (!input)
-    {
-      itkExceptionMacro("Input image required!");
-    }
-    return input->GetLargestPossibleRegion().GetSize();
-  }
-#else
+  /** Get the radius required for interpolation.
+   *
+   * This defines the number of surrounding pixels required to interpolate at
+   * a given point.
+   */
   virtual SizeType
   GetRadius() const = 0;
-#endif
 
 protected:
   InterpolateImageFunction() = default;
diff --git a/Modules/Filtering/Smoothing/include/itkBoxMeanImageFilter.hxx b/Modules/Filtering/Smoothing/include/itkBoxMeanImageFilter.hxx
index 7c591da613e8..c3ecc9297488 100644
--- a/Modules/Filtering/Smoothing/include/itkBoxMeanImageFilter.hxx
+++ b/Modules/Filtering/Smoothing/include/itkBoxMeanImageFilter.hxx
@@ -64,32 +64,9 @@ BoxMeanImageFilter<TInputImage, TOutputImage>::DynamicThreadedGenerateData(
   accImage->SetRegions(accumRegion);
   accImage->Allocate();
 
-#if defined(ITKV4_COMPATIBILITY)
-  // Dummy reporter for compatibility
-  ProgressReporter progress(this, 1, 2 * accumRegion.GetNumberOfPixels());
-#endif
-
-  BoxAccumulateFunction<TInputImage, AccumImageType>(inputImage,
-                                                     accImage,
-                                                     accumRegion,
-                                                     accumRegion
-#if defined(ITKV4_COMPATIBILITY)
-                                                     ,
-                                                     progress);
-#else
-  );
-#endif
-  BoxMeanCalculatorFunction<AccumImageType, TOutputImage>(accImage.GetPointer(),
-                                                          outputImage,
-                                                          accumRegion,
-                                                          outputRegionForThread,
-                                                          this->GetRadius()
-#if defined(ITKV4_COMPATIBILITY)
-                                                            ,
-                                                          progress);
-#else
-  );
-#endif
+  BoxAccumulateFunction<TInputImage, AccumImageType>(inputImage, accImage, accumRegion, accumRegion);
+  BoxMeanCalculatorFunction<AccumImageType, TOutputImage>(
+    accImage.GetPointer(), outputImage, accumRegion, outputRegionForThread, this->GetRadius());
 }
 } // end namespace itk
 #endif
diff --git a/Modules/Filtering/Smoothing/include/itkBoxSigmaImageFilter.hxx b/Modules/Filtering/Smoothing/include/itkBoxSigmaImageFilter.hxx
index e01bf91fc5bb..134e1f11b5ed 100644
--- a/Modules/Filtering/Smoothing/include/itkBoxSigmaImageFilter.hxx
+++ b/Modules/Filtering/Smoothing/include/itkBoxSigmaImageFilter.hxx
@@ -66,32 +66,9 @@ BoxSigmaImageFilter<TInputImage, TOutputImage>::DynamicThreadedGenerateData(
   accImage->SetRegions(accumRegion);
   accImage->Allocate();
 
-#if defined(ITKV4_COMPATIBILITY)
-  // Dummy reporter for compatibility
-  ProgressReporter progress(this, 1, 2 * accumRegion.GetNumberOfPixels());
-#endif
-
-  BoxSquareAccumulateFunction<TInputImage, AccumImageType>(inputImage,
-                                                           accImage,
-                                                           accumRegion,
-                                                           accumRegion
-#if defined(ITKV4_COMPATIBILITY)
-                                                           ,
-                                                           progress);
-#else
-  );
-#endif
-  BoxSigmaCalculatorFunction<AccumImageType, TOutputImage>(accImage,
-                                                           outputImage,
-                                                           accumRegion,
-                                                           outputRegionForThread,
-                                                           this->GetRadius()
-#if defined(ITKV4_COMPATIBILITY)
-                                                             ,
-                                                           progress);
-#else
-  );
-#endif
+  BoxSquareAccumulateFunction<TInputImage, AccumImageType>(inputImage, accImage, accumRegion, accumRegion);
+  BoxSigmaCalculatorFunction<AccumImageType, TOutputImage>(
+    accImage, outputImage, accumRegion, outputRegionForThread, this->GetRadius());
 }
 } // end namespace itk
 #endif
diff --git a/Modules/Filtering/Smoothing/include/itkBoxUtilities.h b/Modules/Filtering/Smoothing/include/itkBoxUtilities.h
index 425c8c3a8479..08b7566a6351 100644
--- a/Modules/Filtering/Smoothing/include/itkBoxUtilities.h
+++ b/Modules/Filtering/Smoothing/include/itkBoxUtilities.h
@@ -99,13 +99,7 @@ void
 BoxAccumulateFunction(const TInputImage *               inputImage,
                       const TOutputImage *              outputImage,
                       typename TInputImage::RegionType  inputRegion,
-                      typename TOutputImage::RegionType outputRegion
-#if defined(ITKV4_COMPATIBILITY)
-                      ,
-                      ProgressReporter & progress)
-#else
-)
-#endif
+                      typename TOutputImage::RegionType outputRegion)
 {
   // type alias
   using InputImageType = TInputImage;
@@ -162,9 +156,6 @@ BoxAccumulateFunction(const TInputImage *               inputImage,
       sum += sIt.Get() * weights[k];
     }
     noutIt.SetCenterPixel(sum + inIt.Get());
-#if defined(ITKV4_COMPATIBILITY)
-    progress.CompletedPixel();
-#endif
   }
 }
 
@@ -207,13 +198,7 @@ BoxMeanCalculatorFunction(const TInputImage *               accImage,
                           TOutputImage *                    outputImage,
                           typename TInputImage::RegionType  inputRegion,
                           typename TOutputImage::RegionType outputRegion,
-                          typename TInputImage::SizeType    radius
-#if defined(ITKV4_COMPATIBILITY)
-                          ,
-                          ProgressReporter & progress)
-#else
-)
-#endif
+                          typename TInputImage::SizeType    radius)
 {
   // type alias
   using InputImageType = TInputImage;
@@ -313,9 +298,6 @@ BoxMeanCalculatorFunction(const TInputImage *               accImage,
           ++(cornerItVec[k]);
         }
         oIt.Set(static_cast<OutputPixelType>(sum / pixelscount));
-#if defined(ITKV4_COMPATIBILITY)
-        progress.CompletedPixel();
-#endif
       }
     }
     else
@@ -378,9 +360,6 @@ BoxMeanCalculatorFunction(const TInputImage *               accImage,
         }
 
         oIt.Set(static_cast<OutputPixelType>(sum / (AccPixType)edgepixelscount));
-#if defined(ITKV4_COMPATIBILITY)
-        progress.CompletedPixel();
-#endif
       }
     }
   }
@@ -392,13 +371,7 @@ BoxSigmaCalculatorFunction(const TInputImage *               accImage,
                            TOutputImage *                    outputImage,
                            typename TInputImage::RegionType  inputRegion,
                            typename TOutputImage::RegionType outputRegion,
-                           typename TInputImage::SizeType    radius
-#if defined(ITKV4_COMPATIBILITY)
-                           ,
-                           ProgressReporter & progress)
-#else
-)
-#endif
+                           typename TInputImage::SizeType    radius)
 {
   // type alias
   using InputImageType = TInputImage;
@@ -502,9 +475,6 @@ BoxSigmaCalculatorFunction(const TInputImage *               accImage,
         }
 
         oIt.Set(static_cast<OutputPixelType>(std::sqrt((squareSum - sum * sum / pixelscount) / (pixelscount - 1))));
-#if defined(ITKV4_COMPATIBILITY)
-        progress.CompletedPixel();
-#endif
       }
     }
     else
@@ -571,9 +541,6 @@ BoxSigmaCalculatorFunction(const TInputImage *               accImage,
 
         oIt.Set(
           static_cast<OutputPixelType>(std::sqrt((squareSum - sum * sum / edgepixelscount) / (edgepixelscount - 1))));
-#if defined(ITKV4_COMPATIBILITY)
-        progress.CompletedPixel();
-#endif
       }
     }
   }
@@ -584,13 +551,7 @@ void
 BoxSquareAccumulateFunction(const TInputImage *               inputImage,
                             TOutputImage *                    outputImage,
                             typename TInputImage::RegionType  inputRegion,
-                            typename TOutputImage::RegionType outputRegion
-#if defined(ITKV4_COMPATIBILITY)
-                            ,
-                            ProgressReporter & progress)
-#else
-)
-#endif
+                            typename TOutputImage::RegionType outputRegion)
 {
   // type alias
   using InputImageType = TInputImage;
@@ -655,9 +616,6 @@ BoxSquareAccumulateFunction(const TInputImage *               inputImage,
     o[0] = sum + i;
     o[1] = squareSum + i * i;
     noutIt.SetCenterPixel(o);
-#if defined(ITKV4_COMPATIBILITY)
-    progress.CompletedPixel();
-#endif
   }
 }
 } // namespace itk
diff --git a/Modules/Filtering/Thresholding/include/itkOtsuMultipleThresholdsCalculator.h b/Modules/Filtering/Thresholding/include/itkOtsuMultipleThresholdsCalculator.h
index 887d562a40b5..d7f6e1a7ab8c 100644
--- a/Modules/Filtering/Thresholding/include/itkOtsuMultipleThresholdsCalculator.h
+++ b/Modules/Filtering/Thresholding/include/itkOtsuMultipleThresholdsCalculator.h
@@ -118,11 +118,7 @@ class ITK_TEMPLATE_EXPORT OtsuMultipleThresholdsCalculator : public HistogramAlg
   SizeValueType m_NumberOfThresholds{ 1 };
   OutputType    m_Output{};
   bool          m_ValleyEmphasis{ false };
-#if defined(ITKV4_COMPATIBILITY)
-  bool m_ReturnBinMidpoint{ true };
-#else
-  bool m_ReturnBinMidpoint{ false };
-#endif
+  bool          m_ReturnBinMidpoint{ false };
 };
 } // end of namespace itk
 
diff --git a/Modules/Filtering/Thresholding/include/itkOtsuMultipleThresholdsImageFilter.h b/Modules/Filtering/Thresholding/include/itkOtsuMultipleThresholdsImageFilter.h
index a065df157749..4bc4165bf290 100644
--- a/Modules/Filtering/Thresholding/include/itkOtsuMultipleThresholdsImageFilter.h
+++ b/Modules/Filtering/Thresholding/include/itkOtsuMultipleThresholdsImageFilter.h
@@ -155,11 +155,7 @@ class ITK_TEMPLATE_EXPORT OtsuMultipleThresholdsImageFilter : public ImageToImag
   OutputPixelType     m_LabelOffset{};
   ThresholdVectorType m_Thresholds{};
   bool                m_ValleyEmphasis{ false };
-#if defined(ITKV4_COMPATIBILITY)
-  bool m_ReturnBinMidpoint{ true };
-#else
-  bool m_ReturnBinMidpoint{ false };
-#endif
+  bool                m_ReturnBinMidpoint{ false };
 };
 } // end namespace itk
 
diff --git a/Modules/Filtering/Thresholding/include/itkOtsuThresholdCalculator.h b/Modules/Filtering/Thresholding/include/itkOtsuThresholdCalculator.h
index 19aecbb7d505..d5cb94e66093 100644
--- a/Modules/Filtering/Thresholding/include/itkOtsuThresholdCalculator.h
+++ b/Modules/Filtering/Thresholding/include/itkOtsuThresholdCalculator.h
@@ -90,11 +90,7 @@ class ITK_TEMPLATE_EXPORT OtsuThresholdCalculator : public HistogramThresholdCal
 
 private:
   typename OtsuMultipleThresholdsCalculator<THistogram>::Pointer m_OtsuMultipleThresholdsCalculator{};
-#if defined(ITKV4_COMPATIBILITY)
-  bool m_ReturnBinMidpoint{ true };
-#else
-  bool m_ReturnBinMidpoint{ false };
-#endif
+  bool                                                           m_ReturnBinMidpoint{ false };
 };
 
 } // end namespace itk
diff --git a/Modules/Filtering/Thresholding/include/itkOtsuThresholdImageFilter.h b/Modules/Filtering/Thresholding/include/itkOtsuThresholdImageFilter.h
index 793eb6925ce0..9e4d0494428a 100644
--- a/Modules/Filtering/Thresholding/include/itkOtsuThresholdImageFilter.h
+++ b/Modules/Filtering/Thresholding/include/itkOtsuThresholdImageFilter.h
@@ -128,13 +128,8 @@ class ITK_TEMPLATE_EXPORT OtsuThresholdImageFilter
     }
   }
 
-
 private:
-#if defined(ITKV4_COMPATIBILITY)
-  bool m_ReturnBinMidpoint{ true };
-#else
   bool m_ReturnBinMidpoint{ false };
-#endif
 };
 
 } // end namespace itk
diff --git a/Modules/Filtering/Thresholding/test/itkOtsuMultipleThresholdsCalculatorTest.cxx b/Modules/Filtering/Thresholding/test/itkOtsuMultipleThresholdsCalculatorTest.cxx
index 79d97e084283..b935e6ea940e 100644
--- a/Modules/Filtering/Thresholding/test/itkOtsuMultipleThresholdsCalculatorTest.cxx
+++ b/Modules/Filtering/Thresholding/test/itkOtsuMultipleThresholdsCalculatorTest.cxx
@@ -81,11 +81,7 @@ itkOtsuMultipleThresholdsCalculatorTest(int argc, char * argv[])
 
   auto otsuThresholdCalculator = OtsuMultipleThresholdCalculatorType::New();
 
-#if defined(ITKV4_COMPATIBILITY)
-  ITK_TEST_EXPECT_TRUE(otsuThresholdCalculator->GetReturnBinMidpoint());
-#else
   ITK_TEST_EXPECT_TRUE(!otsuThresholdCalculator->GetReturnBinMidpoint());
-#endif
 
   otsuThresholdCalculator->SetInputHistogram(histogram);
   otsuThresholdCalculator->SetNumberOfThresholds(numberOfThresholds);
diff --git a/Modules/Filtering/Thresholding/test/itkOtsuMultipleThresholdsImageFilterTest.cxx b/Modules/Filtering/Thresholding/test/itkOtsuMultipleThresholdsImageFilterTest.cxx
index 0e719cb3f1fa..6bbc2c559fb9 100644
--- a/Modules/Filtering/Thresholding/test/itkOtsuMultipleThresholdsImageFilterTest.cxx
+++ b/Modules/Filtering/Thresholding/test/itkOtsuMultipleThresholdsImageFilterTest.cxx
@@ -72,11 +72,7 @@ itkOtsuMultipleThresholdsImageFilterTest(int argc, char * argv[])
 
   // Set up the filter parameters
 
-#if defined(ITKV4_COMPATIBILITY)
-  ITK_TEST_EXPECT_TRUE(filter->GetReturnBinMidpoint());
-#else
   ITK_TEST_EXPECT_TRUE(!filter->GetReturnBinMidpoint());
-#endif
 
   filter->ReturnBinMidpointOff();
 
diff --git a/Modules/Filtering/Thresholding/test/itkOtsuThresholdCalculatorTest.cxx b/Modules/Filtering/Thresholding/test/itkOtsuThresholdCalculatorTest.cxx
index 666d6cd5dda0..86a9e88065d8 100644
--- a/Modules/Filtering/Thresholding/test/itkOtsuThresholdCalculatorTest.cxx
+++ b/Modules/Filtering/Thresholding/test/itkOtsuThresholdCalculatorTest.cxx
@@ -90,12 +90,7 @@ itkOtsuThresholdCalculatorTest(int, char *[])
   auto calculator = CalculatorType::New();
 
   ITK_EXERCISE_BASIC_OBJECT_METHODS(calculator, OtsuThresholdCalculator, HistogramThresholdCalculator);
-
-#if defined(ITKV4_COMPATIBILITY)
-  bool returnBinMidpoint{ true };
-#else
-  bool returnBinMidpoint{ false };
-#endif
+  const bool returnBinMidpoint{ false };
   ITK_TEST_SET_GET_BOOLEAN(calculator, ReturnBinMidpoint, returnBinMidpoint);
 
   calculator->SetInput(histGenerator->GetOutput());
diff --git a/Modules/Filtering/Thresholding/test/itkOtsuThresholdImageFilterTest.cxx b/Modules/Filtering/Thresholding/test/itkOtsuThresholdImageFilterTest.cxx
index 8a791f9b38f4..e1dad12a6886 100644
--- a/Modules/Filtering/Thresholding/test/itkOtsuThresholdImageFilterTest.cxx
+++ b/Modules/Filtering/Thresholding/test/itkOtsuThresholdImageFilterTest.cxx
@@ -62,13 +62,7 @@ itkOtsuThresholdImageFilterTest(int argc, char * argv[])
 
   ITK_EXERCISE_BASIC_OBJECT_METHODS(filter, OtsuThresholdImageFilter, HistogramThresholdImageFilter);
 
-
-#if defined(ITKV4_COMPATIBILITY)
-  ITK_TEST_EXPECT_TRUE(filter->GetReturnBinMidpoint());
-#else
   ITK_TEST_EXPECT_TRUE(!filter->GetReturnBinMidpoint());
-#endif
-
 
   auto numberOfHistogramBins = static_cast<itk::SizeValueType>(std::stoi(argv[3]));
   filter->SetNumberOfHistogramBins(numberOfHistogramBins);
diff --git a/Modules/Remote/Deprecated/NeuralNetworks.remote.cmake b/Modules/Remote/Deprecated/NeuralNetworks.remote.cmake
deleted file mode 100644
index 84fe42f856da..000000000000
--- a/Modules/Remote/Deprecated/NeuralNetworks.remote.cmake
+++ /dev/null
@@ -1,64 +0,0 @@
-#-- # Grading Level Criteria Report
-#-- EVALUATION DATE: 2020-03-01
-#-- EVALUATORS: [<<NO EVALUATOR>>,<<NO EVALUATOR>>]
-#--
-#-- ## Compliance level 5 star (AKA ITK main modules, or remote modules that could become core modules)
-#--   - [ ] Widespread community dependance
-#--   - [ ] Above 90% code coverage
-#--   - [ ] CI dashboards and testing monitored rigorously
-#--   - [ ] All requirements of Levels 4,3,2,1
-#--
-#-- ## Compliance Level 4 star (Very high-quality code, perhaps small community dependance)
-#--   - [ ] Meets all ITK code style standards
-#--   - [ ] No external requirements beyond those needed by ITK proper
-#--   - [ ] Builds and passes tests on all supported platforms within 1 month of each core tagged release
-#--   - [ ] Active developer community dedicated to maintaining code-base
-#--   - [ ] 75% code coverage demonstrated for testing suite
-#--   - [ ] Continuous integration testing performed
-#--   - [ ] All requirements of Levels 3,2,1
-#--
-#-- ## Compliance Level 3 star (Quality beta code)
-#--   - [ ] API | executable interface is considered mostly stable and feature complete
-#--   - [ ] Some tests exist and pass on at least some platform
-#--   - [ ] All requirements of Levels 2,1
-#--
-#-- ## Compliance Level 2 star (Alpha code feature API development or niche community/execution environment dependance )
-#--   - [ ] Compiles for at least 1 niche set of execution envirionments, and perhaps others
-#--         (may depend on specific external tools like a java environment, or specific external libraries to work )
-#--   - [ ] All requirements of Levels 1
-#--
-#-- ## Compliance Level 1 star (Pre-alpha features under development and code of unknown quality)
-#--   - [ ] Code complies on at least 1 platform
-#--
-#-- ## Compliance Level 0 star ( Code/Feature of known poor-quality or deprecated status )
-#--   - [X] Code reviewed and explicitly identified as not recommended for use
-#--
-#-- ### Please document here any justification for the criteria above
-#       This outdated code is not recommended for use. It is not optimized or rigourously tested
-#       This module has not received updates or testing for many many years
-#       Core developers should *NOT* expend energy or resources keeping this codebase consistent with ITK
-
-if(NOT ITK_LEGACY_REMOVE
-   AND ITKV4_COMPATIBILITY
-   AND Module_ITKDeprecated)
-
-  itk_fetch_module(
-    NeuralNetworks
-    "This deprecated remote module contains classes and support classes
-for the calculation of artificial neural networks.
-
-This can be used, for instance, for image classification.
-
-This historical set of features is likely not appropriate for modern neural
-network implementations due to performance issues."
-    MODULE_COMPLIANCE_LEVEL 0
-    GIT_REPOSITORY https://github.com/InsightSoftwareConsortium/ITKNeuralNetworks.git
-    GIT_TAG c293e56699d6d102dcde567baf1cf5b704819c17
-    )
-
-  if(NOT ITK_LEGACY_SILENT AND Module_NeuralNetworks)
-    message(WARNING "NeuralNetworks remote module is deprecated.
-    Development of this module has ended, and it will be removed
-    in future ITK versions.")
-  endif()
-endif()