<script type="text/javascript">
/* This script and many more are available free online at
The JavaScript Source!! http://javascript.internet.com
Created by: Kiran Pai | http://www.codecoffee.com/ */

var bluesplayers= new Array("B.B. King", "Muddy Waters", " Stevie Ray Vaughan", "George Thorogood");
var rockplayers = new Array("Alvin Lee", "David Gilmour", "Pete Townshend", "Jeff Beck");

function set_player() {
  var select_genre = document.myform.genre;
  var select_player = document.myform.player;
  var selected_genre = select_genre.options[select_genre.selectedIndex].value;

  select_player.options.length=0;
  if (selected_genre == "blues"){
    for(var i=0; i<bluesplayers.length; i++)
    select_player.options[select_player.options.length] = new Option(bluesplayers[i]);
  }
  if (selected_genre == "rock"){
    for(var i=0; i<rockplayers.length; i++)
    select_player.options[select_player.options.length] = new Option(rockplayers[i]);
  }
}
</script>


<form name="myform" method="POST">
  <table>
    <tr>
    <td>Genre:</td><td>
    <select name="genre" onchange="set_player()">
    <option value="blues">Select One
    <option value="blues">Blues
    <option value="rock">Rock
    </select>
    </td>
    </tr><tr>
    <td>Guitarist:</td><td>
    <select name="player">
    <option>------
    </select>
    </td></tr>
  </table>
</form>
Test: JAVAScript İndir - Türkçe JAVAScript Kaynağınız

Örnek teşkil eder umarım.