Hi, When using overloaded functions with shared_ptr parameter, overload resolution is often ambigous. It is ambigous in situations where using raw pointers would not be ambigous. I've seen a few workarounds. One workaround is to make one of the two functions a template function, but that does not work in all cases. Another workaround is to just give the functions different names, but you can't do that when the function is a CTOR. Well, to my surprise, I found a post from Artyom Borodkin from last December that explains how it can be permanently fixed in boost itself! I thought there was no way I would ever resolve this. http://lists.boost.org/Archives/boost/2005/12/97817.php I went ahead and tested his suggestion by modifying the boost source (I had to change slightly what he wrote), and it worked! I changed this constructor: template<class Y> shared_ptr(shared_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws { } to this: template<class Y> shared_ptr(shared_ptr<Y> const & r, typename enable_if<typename is_convertible<Y*, T*>::type, void*>::type = 0): px(r.px), pn(r.pn) // never throws { } So to iterate what Artyom said, why would we not want to do this?! Thanks, Phillip Hellewell