I 've noticed this as well. In our application we use a data sample class which gets created and deleted a lot. It is slow because it uses a std::map, which is heavy on creation and deletion. I was thus thinking about making a custom allocator, but item 10 from Meyers 'Effective STL' talked me out of it, especially stating that portable allocators should be more or less stateless. The obvious use of an allocator was to allocate from a special fast (non thread safe) private memory pool. Btw I was trying the stack_alloc allocator but on VS2003 it fails to compile for list and set. I think it is related that the list/set implementation which instantiate it with an incomplete type: Plauger's list code: template<class _Ty, class _Alloc> class _List_nod { // base class for _List_ptr to hold allocator _Alnod protected: struct _Node; friend struct _Node; typedef typename _Alloc::template rebind<_GENERIC_BASE>::other::pointer _Genptr; etc... };