<script src="js/jquery-1.3.2.js"></script> 
<script type="text/javascript"> 
function doit(){
    alert($("input[name='rad']:checked").val());
}
</script> 

<input id="rad" name="rad" type="radio" value="1" /> 
<input id="rad" name="rad" type="radio" value="2" /> 
<input id="rad" name="rad" type="radio" value="3" /> 
<input type="button" onclick="doit()" value="click">