diff --git a/include/llvm/Type.h b/include/llvm/Type.h
index d4f86f0b5c4..4a8bbf03de4 100644
--- a/include/llvm/Type.h
+++ b/include/llvm/Type.h
@@ -268,6 +268,11 @@ public:
   /// This will return zero if the type does not have a size or is not a
   /// primitive type.
   ///
+  /// Note that this may not reflect the size of memory allocated for an
+  /// instance of the type or the number of bytes that are written when an
+  /// intance of the type is stored to memory. The TargetData class provides
+  /// additional query functions to provide this information.
+  ///
   unsigned getPrimitiveSizeInBits() const;
 
   /// getScalarSizeInBits - If this is a vector type, return the