Thirty-five cases of perforated colon diverticulitis were treated by us between 1960 and 1977. An overall mortality of 34% reveals the seriousness of this disease. Perforation in open peritoneum doubles the mortality and morbidity rate of covered perforations and of secondary fistulisation. The surgical operations used--immediate resection or colostomy and a drainage--were imposed by the status of the patient and the local state of the lesion. The resection of the pathological colon segment, when feasable, caused no death in this series although a mortality of 48% was noted for multiple procedures. The diagnostical and surgical difficulties associated to profound biological and hemodynamic alterations in these old patients, justifies the multiple stage surgery in a large number of cases. Resection of the perforated segment remains the treatment of choice.