From 1966 to 1990, 226 consecutive patients were operated on electively for diverticular disease of the sigmoid colon. The indications for surgery were colovesical fistula or suspicion of residual abscess, existence of two or more previous attacks of acute inflammation, existence of chronic symptoms and suspicion of colonic carcinoma. Colonic resection with primary anastomosis was performed in 217 patients with a covering colostomy in 1 case only. The Hartmann procedure was performed in 9 patients with extension of the lesions to the rectum and/or high operative risk. One or more abscesses were found by the surgeon or the pathologist in 50 p. cent of the patients. There were no postoperative deaths, no clinical anastomotic leakages. Long-term results were evaluated for the patients operated on before 1987, with a follow-up from 2 to 22 years. 85 p. cent of the patients had no more symptoms, 11 p. cent complained of persistent symptoms and 3% had recurrent attacks of pain and fever. Colonic barium enema is the best examination for diverticulitis and chronic abscesses. Surgical treatment is easier for abscesses located within the colonic wall and mesentery, than for extracolic abscesses with local peritonitis. Correlations between preoperative symptoms and operative findings are often not good. The good results obtained in 82 p. cent of the patients operated on for chronic symptoms suggest that chronic symptoms should be part of the indications for elective surgery. The low incidence (3 p. cent) of recurrent attacks of pain and fever is in favour of a resection limited to the sigmoid colon even when diffuse colonic diverticula are present.(ABSTRACT TRUNCATED AT 250 WORDS)