I presume you mean remove them from the second list and back to the first list. Try this http://jsfiddle.net/bdMAF/38/
<div>
<h3>List A</h3>
<select id="list1" multiple="multiple" rows=2>
<option value=1>Option 1</option>
<option value=2>Option 2</option>
<option value=3>Option 3</option>
<option value=4>Option 4</option>
</select>
<br/>
<input id="button1" type="button" value="Move to List B" />
</div>
<div>
<h3>List A</h3>
<select id="list2" multiple="multiple" rows=2>
</select>
<br/>
<input id="button2" type="button" value="Move to List A" />
</div>
$(function(){
$("#button1").click(function(){
$("#list1 > option:selected").each(function(){
$(this).remove().appendTo("#list2");
});
});
$("#button2").click(function(){
$("#list2 > option:selected").each(function(){
$(this).remove().appendTo("#list1");
});
});
});