With MediaWiki 1.18 now being deployed to WMF wikis (the final set of wikis is slated to get 1.18 tonight starting at 23:00 UTC), I've heard reports of people using list=categorymembers&cmnamespace=6 and getting an empty result, even though there are files in the category. This is a symptom of the cmnamespace workaround that was introduced about two years ago. However, we now have the cmtype parameter that can be used to replace most uses of cmnamespace, and doesn't suffer from any of its flaws (no nasty hacks to work around slow DB queries, no incomplete or empty results): To only list files, use &cmtype=file (previously &cmnamespace=6) To only list subcategories, use &cmtype=subcat (previously &cmnamespace=14) To only list 'normal' pages that aren't files or subcategories, use &cmtype=page (previously &cmnamespace=0|1|etc|everything|except|six|and|fourteen) You can combine values for cmtype, e.g. &cmtype=file|subcat to list both files and subcategories. The default value for cmtype is file|subcat|page (i.e. list everything). Roan