<script language="JavaScript" type="text/javascript">
 function sortlist() {
 var lb = document.getElementById('mylist');
 arrTexts = new Array();
 
 for(i=0; i<lb.length; i++)  {
   arrTexts[i] = lb.options[i].text;
 }
 
 arrTexts.sort();
 
 for(i=0; i<lb.length; i++)  {
   lb.options[i].text = arrTexts[i];
   lb.options[i].value = arrTexts[i];
 }
 }
 </script>
 
 
 <form action="#">
 <select name=mylist id=mylist size=5>
 <option value="Anton">Anton
 <option value="Mike">Mike
 <option value="Peter">Peter
 <option value="Bill">Bill
 <option value="Carl">Carl
 </select>
 <br>
 <a href="javascript:sortlist()">sort</a>
 </form>