I get GL_INVALID_OPERATION from glAccum. The call is not made between begin and end. Is there any kind of special initialization that is needed to use the accumulation buffer? Is glAcucum a generally supported feature by most OpenGL implementations? I have a Radeon 9800 pro so i'm assuming it should be supported on my card. Anyone know whats going on here? Thanks a lot!

No, I did not do that. Is this all I have to add to my pixel format descriptor?

pfd.cAccumBits = 24;
pfd.cAccumRedBits = 8;
pfd.cAccumGreenBits = 8;
pfd.cAccumBlueBits = 8;
pfd.cAccumAlphaBits = 0;

I'm not getting the error anymore, but nothing shows up on the screen when I do:

glReadBuffer(GL_BACK);
glDrawBuffer(GL_BACK);
glClear(GL_ACCUM_BUFFER_BIT);
glColor3f(1.0, 0.0, 0.0);
DrawCube();
glAccum(GL_ACCUM, 0.5);
glColor3f(0.0, 1.0, 0.0);
DrawCube();
glAccum(GL_ACCUM, 0.5);
glAccum(GL_RETURN, 1.0);

Things show up fine when I don't return the accumulation buffer (when I comment out glAccum(GL_RETURN, 1.0)).

Thanks again!

Edit: I think the accumulation buffer is drawing fine (as I get a grey screen if I do glAccum(GL_RETURN, 0.5)), but I think the scene isn't drawing to the back buffer correctly.

Nevermind, I found out what was wrong .. thanks for the help!! :)