We also experienced a PermGen memory error under Glassfish (which I'm led to believe is partially based on Tomcat). The error seemed to be exacerbated by frequent autodeploys. We tried bumping up our maxPermSize as well, but that only delayed the problem. In the end we appear to have solved this by upgrading to Glassfish (v2.1), but in the case of Tomcat, you could try the AntiJarLocking settings.