Diverticulitis free perforation carries a high mortality rate in the elderly, and this motivates the search for specific prognostic factors. The aim of this study was to assess prognostic factors in patients over 70 years of age that were operated on for generalized peritonitis caused by perforated colonic diverticulitis. A retrospective study in 22 patients was performed: demographic data, American Society of Anaesthesiology grading, site and diameter, degree of perforation according to Hinchey's classification, duration of symptoms, Manheim Peritonitis Index (MPI) score, and surgical treatment were evaluated. Patients over 70 years of age were grouped in deceased and not deceased. In this subgroup, postoperative mortality rate was 40%, and diameter of perforation, duration of symptoms, and MPI score seemed significantly related to postoperative death. In the elderly, prognosis is strongly related to duration of symptoms, and treatment delay is caused by late hospitalization because of a low sensibility to the disease symptoms in old people.