diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa11b32c5ffe..877a367b28b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,11 +5,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ## [2.0.5] - 2022-MM-DD
 ### Added
+- Added `HeteroData.is_undirected()` support ([#4604](https://github.com/pyg-team/pytorch_geometric/pull/4604))
 - Added the `Genius` and `Wiki` datasets to `nn.datasets.LINKXDataset` ([#4570](https://github.com/pyg-team/pytorch_geometric/pull/4570), [#4600](https://github.com/pyg-team/pytorch_geometric/pull/4600))
 - Added `nn.glob.GlobalPooling` module with support for multiple aggregations ([#4582](https://github.com/pyg-team/pytorch_geometric/pull/4582))
 - Added support for graph-level outputs in `to_hetero` ([#4582](https://github.com/pyg-team/pytorch_geometric/pull/4582))
 - Added `CHANGELOG.md` ([#4581](https://github.com/pyg-team/pytorch_geometric/pull/4581))
 ### Changed
-- The `bias` argument in `TAGConv` is now actually apllied ([#4597](https://github.com/pyg-team/pytorch_geometric/pull/4597))
+- The `bias` argument in `TAGConv` is now actually applied ([#4597](https://github.com/pyg-team/pytorch_geometric/pull/4597))
 - Fixed subclass behaviour of `process` and `download` in `Datsaet` ([#4586](https://github.com/pyg-team/pytorch_geometric/pull/4586))
 ### Removed
diff --git a/test/transforms/test_to_undirected.py b/test/transforms/test_to_undirected.py
index 167f6535bf8c..3e7070b5c3c1 100644
--- a/test/transforms/test_to_undirected.py
+++ b/test/transforms/test_to_undirected.py
@@ -53,7 +53,11 @@ def test_hetero_to_undirected():
     data['v', 'w'].edge_attr = edge_attr
 
     from torch_geometric.transforms import ToUndirected
+
+    assert not data.is_undirected()
     data = ToUndirected()(data)
+    assert data.is_undirected()
+
     assert data['v', 'v'].edge_index.tolist() == [[0, 1, 2, 3], [1, 0, 3, 2]]
     assert data['v', 'v'].edge_weight.tolist() == edge_weight[perm].tolist()
     assert data['v', 'v'].edge_attr.tolist() == edge_attr[perm].tolist()
diff --git a/torch_geometric/data/hetero_data.py b/torch_geometric/data/hetero_data.py
index 41d011248840..bf52ad2b2c1b 100644
--- a/torch_geometric/data/hetero_data.py
+++ b/torch_geometric/data/hetero_data.py
@@ -12,6 +12,7 @@
 from torch_geometric.data.data import BaseData, Data, size_repr
 from torch_geometric.data.storage import BaseStorage, EdgeStorage, NodeStorage
 from torch_geometric.typing import EdgeType, NodeType, QueryType
+from torch_geometric.utils import is_undirected
 
 NodeOrEdgeType = Union[NodeType, EdgeType]
 NodeOrEdgeStorage = Union[NodeStorage, EdgeStorage]
@@ -295,6 +296,11 @@ def num_edge_features(self) -> Dict[EdgeType, int]:
             for key, store in self._edge_store_dict.items()
         }
 
+    def is_undirected(self) -> bool:
+        r"""Returns :obj:`True` if graph edges are undirected."""
+        edge_index, _, _ = to_homogeneous_edge_index(self)
+        return is_undirected(edge_index, num_nodes=self.num_nodes)
+
     def debug(self):
         pass  # TODO
 
@@ -481,26 +487,14 @@ def _consistent_size(stores: List[BaseStorage]) -> List[str]:
                 if len(sizes) == len(stores) and len(set(sizes)) == 1
             ]
 
-        data = Data(**self._global_store.to_dict())
+        edge_index, node_slices, edge_slices = to_homogeneous_edge_index(self)
+        device = edge_index.device if edge_index is not None else None
 
-        # Iterate over all node stores and record the slice information:
-        node_slices, cumsum = {}, 0
-        node_type_names, node_types = [], []
-        for i, (node_type, store) in enumerate(self._node_store_dict.items()):
-            num_nodes = store.num_nodes
-            node_slices[node_type] = (cumsum, cumsum + num_nodes)
-            node_type_names.append(node_type)
-            cumsum += num_nodes
-
-            if add_node_type:
-                kwargs = {'dtype': torch.long}
-                node_types.append(torch.full((num_nodes, ), i, **kwargs))
-        data._node_type_names = node_type_names
-
-        if len(node_types) > 1:
-            data.node_type = torch.cat(node_types, dim=0)
-        elif len(node_types) == 1:
-            data.node_type = node_types[0]
+        data = Data(**self._global_store.to_dict())
+        if edge_index is not None:
+            data.edge_index = edge_index
+        data._node_type_names = list(node_slices.keys())
+        data._edge_type_names = list(edge_slices.keys())
 
         # Combine node attributes into a single tensor:
         if node_attrs is None:
@@ -511,39 +505,8 @@ def _consistent_size(stores: List[BaseStorage]) -> List[str]:
             value = torch.cat(values, dim) if len(values) > 1 else values[0]
             data[key] = value
 
-        if len([
-                key for key in node_attrs
-                if (key in {'x', 'pos', 'batch'} or 'node' in key)
-        ]) == 0 and not add_node_type:
-            data.num_nodes = cumsum
-
-        # Iterate over all edge stores and record the slice information:
-        edge_slices, cumsum = {}, 0
-        edge_indices, edge_type_names, edge_types = [], [], []
-        for i, (edge_type, store) in enumerate(self._edge_store_dict.items()):
-            src, _, dst = edge_type
-            num_edges = store.num_edges
-            edge_slices[edge_type] = (cumsum, cumsum + num_edges)
-            edge_type_names.append(edge_type)
-            cumsum += num_edges
-
-            kwargs = {'dtype': torch.long, 'device': store.edge_index.device}
-            offset = [[node_slices[src][0]], [node_slices[dst][0]]]
-            offset = torch.tensor(offset, **kwargs)
-            edge_indices.append(store.edge_index + offset)
-            if add_edge_type:
-                edge_types.append(torch.full((num_edges, ), i, **kwargs))
-        data._edge_type_names = edge_type_names
-
-        if len(edge_indices) > 1:
-            data.edge_index = torch.cat(edge_indices, dim=-1)
-        elif len(edge_indices) == 1:
-            data.edge_index = edge_indices[0]
-
-        if len(edge_types) > 1:
-            data.edge_type = torch.cat(edge_types, dim=0)
-        elif len(edge_types) == 1:
-            data.edge_type = edge_types[0]
+        if not data.can_infer_num_nodes:
+            data.num_nodes = list(node_slices.values())[-1][1]
 
         # Combine edge attributes into a single tensor:
         if edge_attrs is None:
@@ -554,4 +517,53 @@ def _consistent_size(stores: List[BaseStorage]) -> List[str]:
             value = torch.cat(values, dim) if len(values) > 1 else values[0]
             data[key] = value
 
+        if add_node_type:
+            sizes = [offset[1] - offset[0] for offset in node_slices.values()]
+            sizes = torch.tensor(sizes, dtype=torch.long, device=device)
+            node_type = torch.arange(len(sizes), device=device)
+            data.node_type = node_type.repeat_interleave(sizes)
+
+        if add_edge_type and edge_index is not None:
+            sizes = [offset[1] - offset[0] for offset in edge_slices.values()]
+            sizes = torch.tensor(sizes, dtype=torch.long, device=device)
+            edge_type = torch.arange(len(sizes), device=device)
+            data.edge_type = edge_type.repeat_interleave(sizes)
+
         return data
+
+
+# Helper functions ############################################################
+
+
+def to_homogeneous_edge_index(
+    data: HeteroData,
+) -> Tuple[Optional[Tensor], Dict[NodeType, Any], Dict[EdgeType, Any]]:
+    # Record slice information per node type:
+    cumsum = 0
+    node_slices: Dict[NodeType, Tuple[int, int]] = {}
+    for node_type, store in data._node_store_dict.items():
+        num_nodes = store.num_nodes
+        node_slices[node_type] = (cumsum, cumsum + num_nodes)
+        cumsum += num_nodes
+
+    # Record edge indices and slice information per edge type:
+    cumsum = 0
+    edge_indices: List[Tensor] = []
+    edge_slices: Dict[EdgeType, Tuple[int, int]] = {}
+    for edge_type, store in data._edge_store_dict.items():
+        src, _, dst = edge_type
+        offset = [[node_slices[src][0]], [node_slices[dst][0]]]
+        offset = torch.tensor(offset, device=store.edge_index.device)
+        edge_indices.append(store.edge_index + offset)
+
+        num_edges = store.num_edges
+        edge_slices[edge_type] = (cumsum, cumsum + num_edges)
+        cumsum += num_edges
+
+    edge_index = None
+    if len(edge_indices) == 1:  # Memory-efficient `torch.cat`:
+        edge_index = edge_indices[0]
+    elif len(edge_indices) > 0:
+        edge_index = torch.cat(edge_indices, dim=-1)
+
+    return edge_index, node_slices, edge_slices
diff --git a/torch_geometric/data/storage.py b/torch_geometric/data/storage.py
index b3469eeab3a3..1b51571f277b 100644
--- a/torch_geometric/data/storage.py
+++ b/torch_geometric/data/storage.py
@@ -427,7 +427,7 @@ def has_self_loops(self) -> bool:
         return int((edge_index[0] == edge_index[1]).sum()) > 0
 
     def is_undirected(self) -> bool:
-        if self.is_bipartite():  # TODO check for inverse storage.
+        if self.is_bipartite():
             return False
 
         for value in self.values('adj', 'adj_t'):