The aim of this study was to analyse the clinical course, surgical strategy and results in patients with perforated large bowel diverticulitis. Over a 15-year period ending in January 1997, 25 patients (13 males and 12 females; mean age 64.1 years) underwent operation for perforation of acute diverticulitis. Depending on the symptoms, the spreading of the peritonitis and the patient general state, different surgical techniques were performed: primary resection and anastomosis with and without defunctioning colostomy (5), primary left hemicolectomy (1), Hartmann's resection (13), Mikulicz's procedure (4), suture and drainage with diverting colostomy (2). The overall mortality was 16%, while morbidity rate was 44%; these results were strictly related to the severity of clinical manifestations and peritoneal contamination. Therefore it must be stressed that a good surgical timing is essential. Our experience and literature data show that primary resection and anastomosis with and without colostomy have good results when the patient is fit, the sepsis is localized and satisfactory bowel preparation is achievable. By contrast, purulent and faecal peritonitis are still usually best treated by Hartamnn's procedure. Finally, it is submitted to surgeons's experience to choose, at any situation, the best procedure regarding age and general state, local findings and extent of peritonitis.