@andybphotography No. Some *very old* Sigma lenses will only work with Canon film cameras (the worst that will happen if you attach them to a digital SLR is that the camera will show an error message and you need to switch it off and on again after removing the lens). But any lens that worked on the 20D will work on your T3i.
I recently got a Canon Rebel T3i and so far I am really enjoying it. My question is, I have lenses for a Canon EOS 20D.
Will or can the lenses for the 20D be used on the Rebel T3i?
Thank you very much
Andrea