I'm using VS v9, just in case that matters in this case. I'm : using namespace std; using namespace boost; unordered_map< string, uint32_t > xrf1; unordered_map< string, uint32_t >::const_iterator& iter = xrf1.find( "hello" ); This is something I've used many times with the other containers (well, std::map at least), but here I'm getting a conversion error. This is resolved by either removing the reference marker, or removing the const qualifier. Can someone explain this please? I'd always thought that applying const was easily done, and if so, then a reference should be sufficient, right? Unless the const cast is marked as explicit somehow? And as a side(ish) question, is there any real need to worry about have an object versus reference to something like an iterator? I've always tried to use references where I can, but I wonder if I should "just say no" and use regular objects from now on? Thanks, -- Craig Longman If it's not *signed* by me, then please don't assume it *is* from me.