diff --git a/rxjava-core/src/main/java/rx/Scheduler.java b/rxjava-core/src/main/java/rx/Scheduler.java
index afc35b6a32a..22735209cdc 100644
--- a/rxjava-core/src/main/java/rx/Scheduler.java
+++ b/rxjava-core/src/main/java/rx/Scheduler.java
@@ -15,9 +15,18 @@
  */
 package rx;
 
+import static org.mockito.Matchers.*;
+import static org.mockito.Mockito.*;
+
 import java.util.Date;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.junit.Test;
+import org.mockito.InOrder;
+import org.mockito.Mockito;
 
+import rx.concurrency.TestScheduler;
 import rx.subscriptions.Subscriptions;
 import rx.util.functions.Action0;
 import rx.util.functions.Func0;
@@ -71,6 +80,56 @@ public abstract class Scheduler {
      */
     public abstract <T> Subscription schedule(T state, Func2<Scheduler, T, Subscription> action, long delayTime, TimeUnit unit);
 
+    /**
+     * Schedules a cancelable action to be executed periodically.
+     * This default implementation schedules recursively and waits for actions to complete (instead of potentially executing
+     * long-running actions concurrently). Each scheduler that can do periodic scheduling in a better way should override this.
+     *
+     * @param state 
+     *            State to pass into the action.
+     * @param action 
+     *            The action to execute periodically.
+     * @param initialDelay 
+     *            Time to wait before executing the action for the first time.
+     * @param period 
+     *            The time interval to wait each time in between executing the action.
+     * @param unit 
+     *            The time unit the interval above is given in.
+     * @return A subscription to be able to unsubscribe from action.
+     */
+    public <T> Subscription schedulePeriodically(T state, final Func2<Scheduler, T, Subscription> action, long initialDelay, long period, TimeUnit unit) {
+        final long periodInNanos = unit.toNanos(period);
+        final AtomicBoolean complete = new AtomicBoolean();
+  
+        final Func2<Scheduler, T, Subscription> recursiveAction = new Func2<Scheduler, T, Subscription>() {
+            @Override
+            public Subscription call(Scheduler scheduler, T state0) {
+                if (!complete.get()) {
+                    long startedAt = now();
+                    final Subscription sub1 = action.call(scheduler, state0);
+                    long timeTakenByActionInNanos = TimeUnit.MILLISECONDS.toNanos(now() - startedAt);
+                    final Subscription sub2 = schedule(state0, this, periodInNanos - timeTakenByActionInNanos, TimeUnit.NANOSECONDS);
+                    return Subscriptions.create(new Action0() {
+                        @Override
+                        public void call() {
+                            sub1.unsubscribe();
+                            sub2.unsubscribe();
+                        }
+                    });
+                }
+                return Subscriptions.empty();
+            }
+        };
+        final Subscription sub = schedule(state, recursiveAction, initialDelay, unit);
+        return Subscriptions.create(new Action0() {
+            @Override
+            public void call() {
+                complete.set(true);
+                sub.unsubscribe();
+            }
+        });
+    }
+    
     /**
      * Schedules a cancelable action to be executed at dueTime.
      * 
@@ -103,7 +162,7 @@ public Subscription schedule(final Func1<Scheduler, Subscription> action) {
         return schedule(null, new Func2<Scheduler, Void, Subscription>() {
 
             @Override
-            public Subscription call(Scheduler scheduler, Void t2) {
+            public Subscription call(Scheduler scheduler, @SuppressWarnings("unused") Void state) {
                 return action.call(scheduler);
             }
         });
@@ -120,7 +179,7 @@ public Subscription schedule(final Func0<Subscription> action) {
         return schedule(null, new Func2<Scheduler, Void, Subscription>() {
 
             @Override
-            public Subscription call(Scheduler scheduler, Void t2) {
+            public Subscription call(@SuppressWarnings("unused") Scheduler scheduler, @SuppressWarnings("unused") Void state) {
                 return action.call();
             }
         });
@@ -137,7 +196,7 @@ public Subscription schedule(final Action0 action) {
         return schedule(null, new Func2<Scheduler, Void, Subscription>() {
 
             @Override
-            public Subscription call(Scheduler scheduler, Void t2) {
+            public Subscription call(@SuppressWarnings("unused") Scheduler scheduler, @SuppressWarnings("unused") Void state) {
                 action.call();
                 return Subscriptions.empty();
             }
@@ -159,7 +218,7 @@ public Subscription schedule(final Func1<Scheduler, Subscription> action, long d
         return schedule(null, new Func2<Scheduler, Void, Subscription>() {
 
             @Override
-            public Subscription call(Scheduler scheduler, Void t2) {
+            public Subscription call(Scheduler scheduler, @SuppressWarnings("unused") Void state) {
                 return action.call(scheduler);
             }
         }, delayTime, unit);
@@ -176,7 +235,7 @@ public Subscription schedule(final Action0 action, long delayTime, TimeUnit unit
         return schedule(null, new Func2<Scheduler, Void, Subscription>() {
 
             @Override
-            public Subscription call(Scheduler scheduler, Void t2) {
+            public Subscription call(@SuppressWarnings("unused") Scheduler scheduler, @SuppressWarnings("unused") Void state) {
                 action.call();
                 return Subscriptions.empty();
             }
@@ -194,12 +253,79 @@ public Subscription schedule(final Func0<Subscription> action, long delayTime, T
         return schedule(null, new Func2<Scheduler, Void, Subscription>() {
 
             @Override
-            public Subscription call(Scheduler scheduler, Void t2) {
+            public Subscription call(@SuppressWarnings("unused") Scheduler scheduler, @SuppressWarnings("unused") Void state) {
                 return action.call();
             }
         }, delayTime, unit);
     }
 
+    /**
+     * Schedules a cancelable action to be executed periodically.
+     * 
+     * @param action 
+     *            The action to execute periodically.
+     * @param initialDelay 
+     *            Time to wait before executing the action for the first time.
+     * @param period 
+     *            The time interval to wait each time in between executing the action.
+     * @param unit 
+     *            The time unit the interval above is given in.
+     * @return A subscription to be able to unsubscribe from action.
+     */
+    public Subscription schedulePeriodically(final Func1<Scheduler, Subscription> action, long initialDelay, long period, TimeUnit unit) {
+        return schedulePeriodically(null, new Func2<Scheduler, Void, Subscription>() {
+            @Override
+            public Subscription call(Scheduler scheduler, @SuppressWarnings("unused") Void state) {
+                return action.call(scheduler);
+            }
+        }, initialDelay, period, unit);
+    }
+
+    /**
+     * Schedules a cancelable action to be executed periodically.
+     * 
+     * @param action 
+     *            The action to execute periodically.
+     * @param initialDelay 
+     *            Time to wait before executing the action for the first time.
+     * @param period 
+     *            The time interval to wait each time in between executing the action.
+     * @param unit 
+     *            The time unit the interval above is given in.
+     * @return A subscription to be able to unsubscribe from action.
+     */
+    public Subscription schedulePeriodically(final Func0<Subscription> action, long initialDelay, long period, TimeUnit unit) {
+        return schedulePeriodically(null, new Func2<Scheduler, Void, Subscription>() {
+            @Override
+            public Subscription call(@SuppressWarnings("unused") Scheduler scheduler, @SuppressWarnings("unused") Void state) {
+                return action.call();
+            }
+        }, initialDelay, period, unit);
+    }
+
+    /**
+     * Schedules an action to be executed periodically.
+     * 
+     * @param action 
+     *            The action to execute periodically.
+     * @param initialDelay 
+     *            Time to wait before executing the action for the first time.
+     * @param period 
+     *            The time interval to wait each time in between executing the action.
+     * @param unit 
+     *            The time unit the interval above is given in.
+     * @return A subscription to be able to unsubscribe from action.
+     */
+    public Subscription schedulePeriodically(final Action0 action, long initialDelay, long period, TimeUnit unit) {
+        return schedulePeriodically(null, new Func2<Scheduler, Void, Subscription>() {
+            @Override
+            public Subscription call(@SuppressWarnings("unused") Scheduler scheduler, @SuppressWarnings("unused") Void state) {
+                action.call();
+                return Subscriptions.empty();
+            }
+        }, initialDelay, period, unit);
+    }
+
     /**
      * Returns the scheduler's notion of current absolute time in milliseconds.
      */
@@ -207,4 +333,43 @@ public long now() {
         return System.currentTimeMillis();
     }
 
+    public static class UnitTest {
+        @SuppressWarnings("unchecked") // mocking is unchecked, unfortunately
+        @Test
+        public void testPeriodicScheduling() {
+            final Func1<Long, Void> calledOp = mock(Func1.class);
+            
+            final TestScheduler scheduler = new TestScheduler();
+            Subscription subscription = scheduler.schedulePeriodically(new Action0() {
+                @Override public void call() {
+                    System.out.println(scheduler.now());
+                    calledOp.call(scheduler.now());
+                }
+            }, 1, 2, TimeUnit.SECONDS);
+            
+            verify(calledOp, never()).call(anyLong());
+
+            InOrder inOrder = Mockito.inOrder(calledOp);
+            
+            scheduler.advanceTimeBy(999L, TimeUnit.MILLISECONDS);
+            inOrder.verify(calledOp, never()).call(anyLong());
+
+            scheduler.advanceTimeBy(1L, TimeUnit.MILLISECONDS);
+            inOrder.verify(calledOp, times(1)).call(1000L);
+            
+            scheduler.advanceTimeBy(1999L, TimeUnit.MILLISECONDS);
+            inOrder.verify(calledOp, never()).call(3000L);
+            
+            scheduler.advanceTimeBy(1L, TimeUnit.MILLISECONDS);
+            inOrder.verify(calledOp, times(1)).call(3000L);
+            
+            scheduler.advanceTimeBy(5L, TimeUnit.SECONDS);
+            inOrder.verify(calledOp, times(1)).call(5000L);
+            inOrder.verify(calledOp, times(1)).call(7000L);
+            
+            subscription.unsubscribe();
+            scheduler.advanceTimeBy(11L, TimeUnit.SECONDS);
+            inOrder.verify(calledOp, never()).call(anyLong());
+        }
+    }
 }
diff --git a/rxjava-core/src/main/java/rx/concurrency/ExecutorScheduler.java b/rxjava-core/src/main/java/rx/concurrency/ExecutorScheduler.java
index ed40bec3507..a2522a29000 100644
--- a/rxjava-core/src/main/java/rx/concurrency/ExecutorScheduler.java
+++ b/rxjava-core/src/main/java/rx/concurrency/ExecutorScheduler.java
@@ -44,6 +44,27 @@ public ExecutorScheduler(ScheduledExecutorService executor) {
         this.executor = executor;
     }
 
+    @Override
+    public <T> Subscription schedulePeriodically(final T state, final Func2<Scheduler, T, Subscription> action, long initialDelay, long period, TimeUnit unit) {
+        if (executor instanceof ScheduledExecutorService) {
+            final CompositeSubscription subscriptions = new CompositeSubscription();
+            
+            ScheduledFuture<?> f = ((ScheduledExecutorService) executor).scheduleAtFixedRate(new Runnable() {
+                @Override
+                public void run() {
+                    Subscription s = action.call(ExecutorScheduler.this, state);
+                    subscriptions.add(s);
+                }
+            }, initialDelay, period, unit);
+            
+            subscriptions.add(Subscriptions.create(f));
+            return subscriptions;
+            
+        } else {
+            return super.schedulePeriodically(state, action, initialDelay, period, unit);
+        }
+    }
+    
     @Override
     public <T> Subscription schedule(final T state, final Func2<Scheduler, T, Subscription> action, long delayTime, TimeUnit unit) {
         final DiscardableAction<T> discardableAction = new DiscardableAction<T>(state, action);
diff --git a/rxjava-core/src/main/java/rx/concurrency/TestScheduler.java b/rxjava-core/src/main/java/rx/concurrency/TestScheduler.java
index c785031df26..a10ab90e216 100644
--- a/rxjava-core/src/main/java/rx/concurrency/TestScheduler.java
+++ b/rxjava-core/src/main/java/rx/concurrency/TestScheduler.java
@@ -54,11 +54,12 @@ public int compare(TimedAction<?> action1, TimedAction<?> action2) {
         }
     }
 
+    // Storing time in nanoseconds internally.
     private long time;
 
     @Override
     public long now() {
-        return time;
+        return TimeUnit.NANOSECONDS.toMillis(time);
     }
 
     public void advanceTimeBy(long delayTime, TimeUnit unit) {
@@ -79,6 +80,7 @@ private void triggerActions(long targetTimeInNanos) {
         while (!queue.isEmpty()) {
             TimedAction<?> current = queue.peek();
             if (current.time > targetTimeInNanos) {
+                time = targetTimeInNanos;
                 break;
             }
             time = current.time;
@@ -95,7 +97,7 @@ public <T> Subscription schedule(T state, Func2<Scheduler, T, Subscription> acti
 
     @Override
     public <T> Subscription schedule(T state, Func2<Scheduler, T, Subscription> action, long delayTime, TimeUnit unit) {
-        queue.add(new TimedAction<T>(this, now() + unit.toNanos(delayTime), action, state));
+        queue.add(new TimedAction<T>(this, time + unit.toNanos(delayTime), action, state));
         return Subscriptions.empty();
     }
 }
diff --git a/rxjava-core/src/main/java/rx/operators/OperationInterval.java b/rxjava-core/src/main/java/rx/operators/OperationInterval.java
index 19a3736826d..a9a46d2bbe6 100644
--- a/rxjava-core/src/main/java/rx/operators/OperationInterval.java
+++ b/rxjava-core/src/main/java/rx/operators/OperationInterval.java
@@ -20,7 +20,6 @@
 
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -57,47 +56,35 @@ public static Func1<Observer<Long>, Subscription> interval(long interval, TimeUn
     }
 
     private static class Interval implements Func1<Observer<Long>, Subscription> {
-        private final long interval;
+        private final long period;
         private final TimeUnit unit;
         private final Scheduler scheduler;
         
         private long currentValue;
-        private final AtomicBoolean complete = new AtomicBoolean();
 
-        private Interval(long interval, TimeUnit unit, Scheduler scheduler) {
-            this.interval = interval;
+        private Interval(long period, TimeUnit unit, Scheduler scheduler) {
+            this.period = period;
             this.unit = unit;
             this.scheduler = scheduler;
         }
 
         @Override
         public Subscription call(final Observer<Long> observer) {
-            scheduler.schedule(new IntervalAction(observer), interval, unit);
-            return Subscriptions.create(new Action0() {
+            final Subscription wrapped = scheduler.schedulePeriodically(new Action0() {
                 @Override
                 public void call() {
-                    complete.set(true);
+                    observer.onNext(currentValue);
+                    currentValue++;
                 }
-            });
-        }
-        
-        private class IntervalAction implements Action0 {
-            private final Observer<Long> observer;
-            
-            private IntervalAction(Observer<Long> observer) {
-                this.observer = observer;
-            }
+            }, period, period, unit);
             
-            @Override
-            public void call() {
-                if (complete.get()) {
+            return Subscriptions.create(new Action0() {
+                @Override
+                public void call() {
+                    wrapped.unsubscribe();
                     observer.onCompleted();
-                } else {
-                    observer.onNext(currentValue);
-                    currentValue++;
-                    scheduler.schedule(this, interval, unit);
                 }
-            }
+            });
         }
     }
     
diff --git a/rxjava-core/src/main/java/rx/operators/OperationTakeWhile.java b/rxjava-core/src/main/java/rx/operators/OperationTakeWhile.java
index 618e507a441..2941766547b 100644
--- a/rxjava-core/src/main/java/rx/operators/OperationTakeWhile.java
+++ b/rxjava-core/src/main/java/rx/operators/OperationTakeWhile.java
@@ -27,6 +27,7 @@
 import rx.Observer;
 import rx.Subscription;
 import rx.subjects.PublishSubject;
+import rx.subjects.Subject;
 import rx.subscriptions.Subscriptions;
 import rx.util.AtomicObservableSubscription;
 import rx.util.AtomicObserver;
@@ -175,9 +176,8 @@ public Boolean call(Integer input)
 
         @Test
         public void testTakeWhileOnSubject1() {
-            PublishSubject<Integer> s = PublishSubject.create();
-            Observable<Integer> w = (Observable<Integer>) s;
-            Observable<Integer> take = Observable.create(takeWhile(w, new Func1<Integer, Boolean>()
+            Subject<Integer, Integer> s = PublishSubject.create();
+            Observable<Integer> take = Observable.create(takeWhile(s, new Func1<Integer, Boolean>()
             {
                 @Override
                 public Boolean call(Integer input)
diff --git a/rxjava-core/src/main/java/rx/operators/OperatorTester.java b/rxjava-core/src/main/java/rx/operators/OperatorTester.java
index 086affa96da..6fa93c1a1d7 100644
--- a/rxjava-core/src/main/java/rx/operators/OperatorTester.java
+++ b/rxjava-core/src/main/java/rx/operators/OperatorTester.java
@@ -339,6 +339,26 @@ public <T> Subscription schedule(T state, Func2<Scheduler, T, Subscription> acti
                 return underlying.schedule(state, action, dueTime, unit);
             }
 
+            @Override
+            public Subscription schedulePeriodically(Action0 action, long initialDelay, long period, TimeUnit unit) {
+                return underlying.schedulePeriodically(action, initialDelay, period, unit);
+            }
+
+            @Override
+            public Subscription schedulePeriodically(Func0<Subscription> action, long initialDelay, long period, TimeUnit unit) {
+                return underlying.schedulePeriodically(action, initialDelay, period, unit);
+            }
+
+            @Override
+            public Subscription schedulePeriodically(Func1<Scheduler, Subscription> action, long initialDelay, long period, TimeUnit unit) {
+                return underlying.schedulePeriodically(action, initialDelay, period, unit);
+            }
+
+            @Override
+            public <T> Subscription schedulePeriodically(T state, Func2<Scheduler, T, Subscription> action, long initialDelay, long period, TimeUnit unit) {
+                return underlying.schedulePeriodically(state, action, initialDelay, period, unit);
+            }
+
             @Override
             public long now() {
                 return underlying.now();