We're using smart pointers, and due to the way that they are created, we wish to hide the functionality behind a static create() function for each class. That way, the callers only need call create() and they have a smart_pointer to a new object, without having to worry too much about implementation details. So, this has been working fine, until I tried doing some polymorphism. Basically, we have a smart pointer to a base class, where the derived class is chosen at run time, (based on what the caller wants to do). The base class is pure virtual, so we don't know, (or care to know) how the child class implements its functionality. The following code illustrates what I'm trying to do: #include <iostream> #include // Base class class base { public: typedef boost::shared_ptr<base> SharedPtr; ~base(){}; virtual void foo(){ std::cout << "base" << std::endl;}; static SharedPtr create(){ return SharedPtr(new base); }; protected: base(){}; }; // Derived class class d1 : base { public: typedef boost::shared_ptr<d1> SharedPtr; ~d1(){}; void foo() {std::cout << "derived 1" << std::endl;}; static SharedPtr create() { return SharedPtr(new d1); }; protected: d1(){}; }; int main() { base::SharedPtr bsp; d1::SharedPtr d1sp = d1::create(); d1sp->foo(); // This is producing the error. I want to upcast my d1::SharedPtr to a // base::SharedPtr, so that it can be stored, and the reference count // is still intact bsp = boost::static_pointer_cast<base>(d1sp); } And here is the error that I'm getting (from Visual Studio 2003) c:\Program Files\boost\boost_1_35_0\boost\shared_ptr.hpp(222) : error C2243: 'static_cast' : conversion from 'd1 *const' to 'boost::shared_ptr<T>::element_type * with [T=base]' exists, but is inaccessible; c:\Program Files\boost\boost_1_35_0\boost\shared_ptr.hpp(513) : see reference to function template instantiation 'boost::shared_ptr<T>::shared_ptr<d1>(const boost::shared_ptr<d1> &,boost::detail::static_cast_tag) with [T=base]' being compiled; c:\Documents and Settings\td26134\Desktop\trunk1\main.cpp(54) : see reference to function template instantiation 'boost::shared_ptr<T> boost::static_pointer_cast(const boost::shared_ptr<d1> &) with [T=base]' being compiled Thanks.. --dw