UE> shared_ptr: UE> - Size of the shared_ptr object itself is two pointers. UE> - One additional allocation overhead for shared count, weak count and deleter UE> function pointer (I'm just guessing, is that right?) Further, size is how UE> much? Does it have a specially adapted allocator for those? UE> - Additional freedom with custom deleters. UE> - Allows various type conversions (like raw pointers), including to void or UE> other incomplete types. UE> - Allows weak references (i.e. observers rather than owners) via weak_ptr. UE> - Can be constructed from auto_ptr. UE> - Can be retrieved via 'this', but this requires additional overhead UE> (enable_shared_from_this) in the object itself. I would add that shared_ptr can be safely passed between dll's which have different heaps as shared_ptr contains a custom deleter. This is a very important feature. Valentin