I don't think they have a public one but there is one if your
institution has Firstsearch.

http://www.oclc.org/support/documentation/firstsearch/z3950/fs_z39_config_guide/default.htm

"The production server provides access to all the databases available
and requires a valid FirstSearch authorization."

http://www.oclc.org/support/documentation/firstsearch/z3950/z3950_databases/specs/worldcat.htm

Ryan Eby

On 8/22/06, Eric Lease Morgan <[log in to unmask]> wrote:
> Is there a public Z39.50/SRU/SRW/Web Services interface to WorldCat
> or OpenWorldCat?
>
> I would like to create a simple search engine to query "Other's
> books", and *Cat seems like a great candidate.
>
> Inquiring minds would like to know.
>
> --
> Eric Morgan
>