<form action="#">
<p>プルダウンのサイズ変更:
<label for="szz5"><input type="radio" id="szx5" name="szx" value="5" onclick="fSetSelectSizeDOM(this.value)" />5</label>
<label for="szz4"><input type="radio" id="szx4" name="szx" value="4" onclick="fSetSelectSizeDOM(this.value)" />4</label>
<label for="szz3"><input type="radio" id="szx3" name="szx" value="3" onclick="fSetSelectSizeDOM(this.value)" />3</label>
<label for="szz2"><input type="radio" id="szx2" name="szx" value="2" onclick="fSetSelectSizeDOM(this.value)" />2</label>
<label for="szz1"><input type="radio" id="szx1" name="szx" value="1" onclick="fSetSelectSizeDOM(this.value)" />1(デフォルト)</label>
</p>
<p>
<select id="selS2">
<option value="0">-----------</option>
<option value="1">アイテム1</option>
<option value="2">アイテム2</option>
<option value="3">アイテム3</option>
<option value="4">アイテム4</option>
<option value="5">アイテム5</option>
</select>
</p>
</form>
<script type="text/javascript">
function fSetSelectSizeDOM(num){
var sObj=document.getElementById("selS2");
sObj.size=num;
}
</script>