From 1975-1989 55 patients were operated on for complicated diverticular disease at our unit. Intraoperative we found the following complications: 21 walled of perforations, 22 stenosis of the sigmoid colon combined with obstruction of the small and/or large bowel, 8 free perforations with generalized, faecal peritonitis, 7 diverticular fistulae (5 colovesical, 1 colojejunal and 1 colocutaneous fistula) and diverticular bleedings. In 33 cases we performed a resection with primary anastomosis (8 times with protecting stoma). 17 times the Hartmann's procedure was carried out and 5 times a transverse colostomy and drainage was elected. Lethality was 20% and morbidity came to 25%. We consider the primary resection with primary anastomosis to be the procedure of choice for complicated diverticulitis except for free perforation with generalized and faecal peritonitis where we prefer the Hartmann's procedure.