I have two RadListBox controls on my page. These controls are inside an UpdatePanel. There are few other controls on the page, just a couple of radio buttons. I am transferring items in the left list to the right list in the standard way, according to the sample. The left (or source) list contains about 300 items. Each item is defined by an item template. The item template defines a table with two columns (table name, field name). The data in that list is coming from a declaratively bound objectdatasource. I have tried various combinations of property setting/clearing on the list control but cannot get very good performance in any case. It takes about 2.5 seconds for the list control to completely reflect that a new item has been selected. Further, it takes about 3 seconds for the tranfer from the left to the right list control to complete. There does not appear to be any postbacks occuring nor is there any data 'rebinding' occuring. Why would this control's performance be so dodgy for only a couple of hundred items? Am I missing some finer point? Note that I have seen a similar post where a user had performance problems as well, but that was for 15,000 items. I can reasonably see a problem occuring in that scenario. Also note that when I programmatically limit the data returned from the objectdatasource (and thus into the source list control) to say 10 or 20 items, the performance is much better. Finally, note the performance of the ASP.NET list control is very good in this scenario, but you cannot replicate multiple columns on that list control without resorting to custom string formatting and the use of fixed width fonts. Thanks.