Looks like a bit of a hole in the APIs, along with a bit of confusion as to how to proceed. Actually, you're lucky: I didn't find the addUserToGroup method, and had to hack it by hand. The way it's done is to find an XWikiObject of class "XWiki.XWikiGroups" in the document whose name is that of the group and remove that object from that document. For example, If user 'XWiki.GunterLeeb' is a member of a group named 'XWiki.Dept999Group', that is represented by a document named XWiki.Dept999Group containing an XWiki.XWikiGroups object whose 'member' field contains the value 'XWiki.GunterLeeb'. Simple, no? To remove XWiki.GunterLeeb from XWiki.Dept999Group, you must do something like this (assuming that context is the XWikiContext passed to you and xwiki is the return from context.getWiki()): String groupName = "Xwiki.Dept999Group"; String wikiName = "XWiki.GunterLeeb"; String groupClassName = xwiki.getGroupClass().getName(); // Get the XWiki document holding the objects comprising the group membership list XWikiDocument groupDoc = xwiki.getDocument(groupName, context); // Get the specific group membership object for the user BaseObject groupObj = groupDoc.getObject(groupClassName, "member", wikiName); /* * This code imitates something I found in the XWiki code that seemed * to be necessary, but appears superfluous: get all the group membership * objects as a Vector and null the entry containing this one */ Vector objects = doc.getObjects(groupClassName); objects.set(obj.getIntValue("id"), null); // This removes the object from the group document. groupDoc.addObjectsToRemove(groupObj); xwiki.saveDocument(doc, context); /* * This may not be necessary, but the group service does have * a cache, and I've found that adding or removing entries * sometimes don't take effect if I don't do this. */ xwiki.getGroupService().flushCache(); This is how my servlet filter accomplishes this; if any of the developers can critique this, I'd appreciate it, especially the bits that looked just a little suspicious to me. brain[sic]