How do I get completion to only match certain types of files

[Gregory Gerard <ggerard@xxxxxxxxxxxxxxxxxxxxxx>]

I would like to restrict the 'cd' command so that it can only complete 
directories (or shell variables).  Other file types (like links, devices, 
etc.) would be gravy, but not necessary.  I could do the restriction in 
tcsh, but tcsh has other problems that caused me to switch to zsh.

While browsing the man page, I saw I could restrict to named directories, 
but that's not really a help.

Am I missing something in the docs?

thanks for the help,
greg