Ref: http://www.aspsnippets.com/Articles/Using-JavaScript-with-ASP.Net-RadioButtonList-Control.aspx
<script type = "text/javascript">
function GetSelectedItem() {
var RB1 = document.getElementById("<%=RadioButtonList1.ClientID%>");
var radio = RB1.getElementsByTagName("input");
var label = RB1.getElementsByTagName("label");
for (var i = 0; i < radio.length; i++) {
if (radio[i].checked) {
alert("SelectedText = " + label[i].innerHTML);
alert("SelectedValue = " + radio[i].value);
}
}
return false;
}
</script>