function checkAll(field) { for (i = 0; i < field.length; i++) field[i].checked = true ; } function uncheckAll(field) { for (i = 0; i < field.length; i++) field[i].checked = false ; } HTML Part <input type="button" name="CheckAll" value="Check All" onclick="checkAll(document.myform.list)"> <input type="button" name="UnCheckAll" value="Uncheck All" onclick="uncheckAll(document.myform.list)">