Between 1962 and 1977 approximately 2% of Denver kidney transplant patients developed colon perforation. The single commonest cause was diverticulitis of the left colon (6/13 cases). In spite of drastic reduction or discontinuation of immunosuppression, only 5/13 patients survived for more than 90 days after operation. Analysis of this experience suggests that the high mortality rate associated with this complication can be reduced by early operation which removes the perforation from the peritoneal cavity (either exteriorization or resection) without primary intestinal reanastomosis. We believe that candidates for kidney transplantation with a history of previously symptomatic diverticulosis coli should have elective colon resection prior to transplantation. Any kidney transplant patient with lower abdominal signs should be investigated and treated aggressively.