There is only one tree in the repository, but as it is impossible to work on different versions of the same file in the same file at the same time (unless you work in the quantum world ;-) then you'll have to check out the different versions to different places. Of course you can also flip between versions on a subdirectory level, you don't have to keep two trees or two full trees if you don't want to. But it can easily get messy if you are not careful. With two trees you can still see that they are 'one' source tree because you can do cd xemacs-21.2; cvs tag start_myfix INSTALL; <edit INSTALL> cvs commit -m "Corrected configure instructions" INSTALL cd ../xemacs-22.0; cvs -q update -jstart_myfix -jrelease-21-2 INSTALL cvs commit -m "merged fixes from 21.2 branch to 22.0 branch" instead of re-implementing the changes in the second branch. For people with only read access (e.g. like me) the fact that the two versions exist in the same source tree at the repository is of no big importance (except for the fact that it's good to know :-) - Tor (jumping in with too many cvs comments maybe.. it's a habit I guess, I'm responsible for the cvs stuff where I work)