Hi, The above idea is right, but there's small bug - as you can see watching HTML source code, ASP.NET creates RadioButton control as SPAN tag which contains INPUT and LABEL controls. Knowing that we must change the className attribute for that SPAN control, which unfortunately doesn't have an ID. The solution to this is to get INPUT’s control parent tag and change its className. The JavaScript code should look like that: // call this function to change colors function changeRadiobuttonsColorClasses() { changeRadiobuttonColorClass("rbNo", "clBgColorRed"); changeRadiobuttonColorClass("rbYes", "clBgColorGreen"); } // This function change className for control. // Params: // controlName - name of the control // className - new class name to set function changeRadiobuttonColorClass(controlName, className) { // first - find the control var el = document.getElementById(controlName); // if result is NULL, there's no control on the page if (el == null) return; // Now, find control's parent tag (should be SPAN). var elParent = el.parentNode if (elParent != null) elParent.className = className; } To assign JavaScript to control’s action you can simply type: onclick=” changeRadiobuttonsColorClasses()” in the control’s tag. -- Mariusz 'mAv' Wójcik master e-software engineer