I tried to extract the functionality from my app and created a simple example out of it, just like Peter suggested. Seems like all is well there. Validation occurs, and transaction rollback happens when an exception is thrown or the @Rollback is triggered. Apparently, I'm doing something wrong elsewhere. Gavin, I don't actually use Seam validation (yet), but JSF validation instead. Can this introduce any problems? It seemed to work fine in my simple app, so I don't think that's my cause of error. But then, I'm wrong about many things, apparently ;-) Thanks for the quick reactions, I'll try to dig a bit deeper to find my bug. The pain is that, sometimes, the value is changes in the DB, but not always, which makes it very hard to determine the cause of error. By the way: I'm causing the rollback artificially, just to test what will happen when something goes wrong while the update() method in invoked. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4052918#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...