Folks, What is the best way to pass a std::vector<boost::shared_ptr<Derived> > to a function that expects a std::vector<boost::shared_ptr<Base> >? Can I use a cast or should I create a new std::vector<boost::shared_ptr<Base> > by iterating over the std::vector<boost::shared_ptr<Derived> >? Here is some sample code. What f is doing is not important it is just an example: class A { // This class is from a library I have no control over. public: virtual string getName() { return string("A");} }; class B : public A { // I need to create B from A to have extra functionality public: virtual string getName() { return string("B");} virtual string getLongName() { return string("This is B");} }; void f(std::vector<boost::shared_ptr<A> > &v) { // This function is from a library that I have no control over. for(int i = 0; i < v.size(); i++) cout << v[i]->getName(); } int main(char *argv, int arc) { std::vector<boost::shared_ptr<B> > bvec(10); boost::shared_ptr<B> bPtr(new B); bvec[0] = bPtr; f(bvec); // This should not compile. <------------------------- } The last line (with the arrow) won't compile because std::vector<boost::shared_ptr<B> > cannot be converted to std::vector<boost::shared_ptr<A> >.