Colonic complications of renal transplantation occur in 1.9 per cent of the cases. In our series of 587 consecutive renal transplants recipients 3 (0.51 per cent) had colonic complications, including 2 with ischemic colitis and 1 with pseudomembranous colitis. A review of 8 large series describing 2,539 additional renal transplant patients revealed 55 with significant colonic complications. The most common complication was ischemic colitis, which occurred in 29 patients, followed by diverticulitis in 17, pseudomembranous colitis in 5, appendicitis in 3, hemorrhagic proctitis in 1, a disrupted appendiceal stump in 1 and fecal impaction in 1. Etiological factors that may be important in the development of these colonic complications are uremia, blood volume redistribution, immunosuppressive therapy, antibiotic therapy, irradiation and previous retroperitoneal surgery.