Help: Apache and Tomcat

I've set up Tomcat to run with Apache. I'm trying to use Apache's authentication to limit access to servlets. I'm having trouble passing the authentication info from Apache through to Tomcat. If anyone has had experience with this and could give me some help that would be great :).

use the apache directory or file directive

Apache is configured fine. The problem is that I can't get Tomcat to pick up the environment variables such as RemoteUser. At the moment they just come up blank.