<input type="radio" name="aaa" value="1" checked="true">aaa
<input type="radio" name="aaa" value="2">bbb
<input type="radio" name="aaa" value="3">ccc
<input type="button" value="ok" onclick="doTest()">
<script language="JavaScript">
<!--
function doTest(){
alert($("input[name='aaa'][checked]").val());
}
//-->
</script>
