codice:
<?xml version="1.0" encoding="iso-8859-1"?>

  <!DOCTYPE html 
     PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

  <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
    <head>
      <title>Code Example by DYNAMIC+</title>

      <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
      <meta http-equiv="Content-Language" content="en-us" />

      <script type="text/javascript">
      <!--

        var _jobPerSex = new Array( );
        _jobPerSex['maschio'] = new Array( "Architetto", "Geometro", "Attore", "Casalingo", "Avvovocato", "Gi***ò :P" );
        _jobPerSex['femmina'] = new Array( "Architetta", "Geometressa ;)", "Attrice", "Casalinga", "Avvovocata", "Pr*******a :P" );


        function getSexAndPopulate( __objSexSelect )
        {
          var _objJobSelect  = __objSexSelect.form.elements['professione'];
          var _szSelectedJob = __objSexSelect.options[__objSexSelect.selectedIndex].value.toLowerCase( );
          var _jobList       = _jobPerSex[_szSelectedJob];

          _objJobSelect.options.length = 0;

          for ( var i=0; i < _jobList.length; i++ )
            _objJobSelect.options[_objJobSelect.length] = new Option( _jobList[i], _jobList[i] );
          
        }
       
      //-->
      </script>

    </head>
    <body onload="getSexAndPopulate( document.forms['anagrafica'].elements['sesso'] );">

      <div>
        <form name="anagrafica" action="#">

          Sesso:
          <select name="sesso" onchange="getSexAndPopulate( this );">
            <option value="maschio" selected="selected">Maschio</option>
            <option value="femmina">Femmina</option>
          </select>

          Professione:
          <select name="professione">
          </select>

        </form>
      </div>

    </body>
  </html>