Not quite an EJB question but I'll try to help. As far as I remember the validwhen rule was considered to be far too complex in order to be implemented on the client side as well. If you'd like you can try to generate the client scripts as well and view the generated scripts from within the client browser. Finally you can try some debugging on your own, but again I won't be surprise to conclude that the client validation is not working at all. As a final solution I would recommand you to post a similar question on the Struts forum. Regards.