The interface of RadButton for ASP.NET AJAX is level AAA accessible (in compliance with the W3C Web Accessibility Guidelines 2.0) as well as Section 508 compliant. It passes the check of the WAVE automated content compliance tool for Section 508 and WCAG 2.0 - Compliance Level AAA.
When ToggleType="CheckBox" , "Radio" or "Link" and if the Text property is set, the Button compliance level is A.
The control is also visible in Windows High Contrast mode when rendered with Simple skin.
It also offers Keyboard support.