For the end user, the DropDownCheckList resembles an HTML <select> box that when clicked presents available options as checkboxes. The display box lists the checked options, with developer-defined list separators and the ability to append an ellipsis or other text when the listed options exceed the display width. This article presents the common properties and methods of the control and describes the choice to subclass CheckBoxList both in terms of the benefits gained from this inheritance and essential issues faced as a result. Challenges that were resolved through client-side Javascr ipt are also presented, including the display of the ellipsis when necessary, and the employing of document click handlers to automatically collapse a list when a click occurs outside it. The latter and a borrowed shim technique are particularly useful when developing custom drop-down web controls.