To the Editor.—While theoretically the circular muscle of an end colostomy might be expected to produce some sphincteric effect, in actuality it does not. No end colostomy acts as a true sphincter; continence is never present. An end colostomy when primarily matured, with or without an antimesenteric slit, functions the same way. The short antimesenteric slit simply facilitates eversion of a small-diameter colon, so that the colostomy may be fashioned to protrude above skin level as a short nipple. The circular muscle below the slit still produces the same nebulous sphincteric effect that it would if no slit had been made. Any apparent sphincter function arises from the action of the muscles of the abdominal wall through which the colostomy is drawn.