Hi ! I am currently working on a large software involving VS 2010 and a bunch of classes. I'm having a lot of compilation errors C2061 about the class A. All these errors are in header files involving pointer to that class A. I checked not having circular references. I have forward reference to that class A at the top of each concerned header and just after "#include ...". When moving the forward reference to the class A just before the lineinvolving the pointer I don't have compilation error any more. Could you please tell me why it's so ? Many thanks.