In most asp.net applications users experience post backs as a result of submit action by the client browsers. These post backs can be quite annoying when just a small part of the page needs to be refreshed. Update panels are designed to perform partial post back eliminating the need for doing a complete post back for updating a part of the page. But are these post backs truly partial? In this article we try to find out if Update panels actually improve performance by doing partial post backs or do they end up degrading it.