The influence of age and severity of peritonitis was studied in 111 (16%) out of a total of 694 patients treated for diverticular disease. These 111 patients had complications of the disease and were operated upon by four different approaches. The outcome after surgery was expressed as 30 days mortality, number of operations and postoperative complications per patient, overall hospital stay and number of permanent colostomies in surviving patients. The overall hospital stay lasted significantly longer for patients older than 70 years compared to the younger patients (64 versus 41 days). The complications per patient increased significantly from 1.0 to 1.9 and from 1.1 to 2.7 respectively for an age above 70 years and for peritonitis. Preoperative risk factors as age and peritonitis adequately predict the outcome after surgery for complicated diverticular disease. The type of surgery employed seems more dependent on the perioperative findings than on the superiority of one of the procedures.