Finding PrimaryKey columns of a table - Mailing list pgsql-general

Is there a query I can run against the pg system tables to figure out what
columns of the table make up the primary key?

I've messed around w/ psql -E (which is very cool btw) and can't seem to
find the exact query I'm looking for.  I can get all indexes for a table,
but I can't seem to limit the result set to only the primary key.

Am I missing something obvious ?

Thanks
Steve