Twelve patients with chronic renal failure and polycystic kidney disease represent 8% of the 151 hemodialysis patients followed up at the Chromalloy American Kidney Center, Washington University School of Medicine. Ten (83%) of these patients have diverticulosis, and four of these patients developed gross colonic perforation secondary to diverticulitis. Barium enemas on 31 chronic renal failure patients without polycystic kidney disease revealed diverticulosis in 10 (32%). None had diverticulitis. Barium enemas in 120 age-matched non-renal failure control patients revealed diverticulosis in 45 (38%). Non had diverticulitis. These findings suggest that patients with chronic renal failure due to polycystic kidney disease have a high incidence of diverticulosis and diverticulitis, that diverticulosis occurs in patients with chronic renal failure without polycystic kidney disease at a rate similar to that in the general population, and that diverticulitis should be an initial consideration in the differential diagnosis of abdominal pain in patients with polycystic kidney disease.