AIM: Diverticulitis free perforation still remains a major life-threatening condition. Herein we evaluate factors influencing prognosis of patients with perforated colonic diverticulitis and the current validity of Mannheim Peritonitis Index (MPI) in predicting mortality. MATERIAL OF STUDY: From January 2000 to October 2010, 39 patients were operated on for generalized peritonitis from perforated diverticulitis RESULTS: Five postoperative deaths (12.8%) related to septic shock occurred. A cross-sectional study between deceased and non-deceased patients was carried out. Deceased patients were significantly older than non-deceased (76.4 vs. 59.1 years, p=0.019); duration of symptoms was longer in deceased patients (102 vs. 26.9 hours, p=0.000); MPI was higher in deceased patients (31.4 vs. 21.2, p=0.000). Age, duration of symptoms and MPI were independent risk factors predicting poor prognosis. The highest sensitivity and specificity of MPI in predicting mortality was shown for a score >27. CONCLUSIONS: MPI is still effective in predicting postoperative mortality. People who nurse older persons must pay higher attention to complaints in order to reduce the delay in hospitalization.