In 1995-96, 148 patients with the diagnosis diverticulitis of the colon were admitted a total of 176 times to the Department of Gastroenterologic Surgery at Ullevaal Hospital in Oslo. Data on treatment and outcome were recorded retrospectively from patient files. 92% of the hospitalisations were emergency cases of abdominal pain. In 113 hospitalisations, patients were initially treated with intravenous antibiotics, aspiration of the stomach, later oral antibiotics. No deaths were recorded. In 8 out of 64 patients (13%) hospitalised with diverticulitis for the first time, the diagnosis could not be verified by coloscopy or bowel enema. In 63 hospitalisations (36%), the patients underwent surgery. Hartmann's procedure was performed in 31 out of 49 emergency cases. 22 patients undergoing surgery in an emergency setting had perforated diverticulitis; 5 of these patients died within 15 days. 14 patients had planned surgery with bowel resection and 15 patients had a planned closing of the stoma. Two of these 29 patients died post-operatively. Acute diverticulitis is a serious condition, especially when the bowel has perforated. Complications develop both after emergency and elective surgery. We recommend careful selection of patients.