An apparatus to create continence in an end left-sided colostomy in dogs is assessed. The device consists of a samarium-cobalt magnetic ring encased in methyl methacrylate and a magnetic cap. The ring is implanted in the abdominal wall and the colon delivered through it and matured to the skin. The stoma is later obturated by the magnetic cap to provide continence. Ten dogs exposed to "uncoated" samarium-cobalt magnets for periods of up to eight months showed no elevation of cobalt levels in the serum or tissues and no histopathologic changes on postmortem examination. In twelve dogs, magnetic rings were used to create continent colostomies. Eleven of twelve dogs followed for periods up to eight months were continent and tolerated the appliance well. One ring was extruded after a peristomal skin dehiscence occurred. Two skin strictures appeared and were readily controlled by digital dilatation. Sinus, fistula, or infection were not seen. Clinical application of this device is discussed.