I just tried latexdiff, and it choked on either xypic or pb-diagram code. And I don't think Tim's wdiff trick will handle changes like \begin{foo} Stays the same. \end{foo} changing to \begin{bar} Stays the same. \end{bar} since it will put braces around the \begin{...} commands which will mess up the nesting. Are there any other options people know of? What about something that compares dvi or pdf files?? Dan