Upon upgrading to Snow Leopard, I tried to compile a LaTeX document on the command line (i.e. xterm), but a -bash error came up and told me that the "latex" command did not exist. I soon discovered that other commands like xdvi were not recognized. After I confirmed that my TeX distribution had not been deleted (compiling documents using the front-end editor TeXShop worked fine) I went to the MacTeX website FAQ, located here:
http://www.tug.org/mactex/faq/ and discovered (in the answers to question 10) that upgrading to Snow Leopard probably resulted in the removal of /usr/texbin from the default PATH (this is what allows xterm to cross-reference the executable files like latex, xdvi, etc., which are installed by the MacTeX distribution and placed in the directory /usr/texbin). Obviously, without knowing where to look, your computer won't be able to find and execute the commands. The solution to this problem--which was effective after performing the suggested steps and restarting Terminal--is outlined in section (d) of question 10.
