Three types of colonic sphincter substitutes were placed at an abdominal colostomy in dogs. Simple valve construction (8) was based on orthograde intussusception of the colon over 3.5 cm. In calibrated valves (6) the intraluminal pressure was increased by reducing the diameter of the overlying muscle coat. Reverse smooth muscle plasties (5) and simple colostomies (5) served as controls. Immediately after construction highest pressure (50 ± 8.9 mm Hg) was obtained in calibrated valves. After 1 month the pressure dropped to 20 mm Hg, but remained stable thereafter. Although valvular constructions cannot maintain high pressure, they may be useful as substitutes for the internal anal sphincter by filling up the lumen so that the action of a surrounding striated muscle ring becomes more effective