Background & Objectives: Peritonitis due to hollow viscous perforation is one of the most common surgical emergencies attended by a surgeon on duty. Despite many advances in anti-microbial and supportive care, the mortality rate of diffuse peritonitis remains unacceptably high (10-20%). The treatment of peritonitis and the evaluation of different therapeutic approaches are hampered by lack of precise classification. A scoring system should be able to assess the need, type and quality of the care required for a particular patient. Realizing the need for a simple accurate scoring system in these conditions the present study was undertaken to evaluate the prognosis in patients with perforation peritonitis using Mannheim Peritonitis Index. Materials & Methods: Single centered, observational analytical study conducted in Jubilee Mission Medical College & Research Institute. In our study, we have included 64 patients after meeting the inclusion criteria. As per the study protocol, patient data was collected at the time of admission and intra operatively in the Surgery Department. Mannheim Peritonitis Index score was applied to assess the outcome and data analyzed. Results and Discussion: Out of 64 patients studied, statistically significant correlation was observed between incidence of mortality and the risk factors namely, age more than 50 yrs.(25.9%), presence of organ failure(36.4%), preoperative duration more than 24 hrs.(18.6%), diffuse peritonitis(18.2%) and feacal exudates (45.5%). No statistically significant correlation was observed between incidence of mortality and the risk factors namely female sex, non-colonic origin of sepsis, presence of malignancy. Conclusion: In our study population, all risk factors included in the Mannheim Peritonitis Index namely presence of organ failure; preoperative duration> 24hrs; age>50 years, generalized extension of peritonitis and type of exudate had significant association with adverse outcome while in patients with the non-colonic origin of sepsis, presence of malignancy and of the female sex there was no significant association of these risk factors with adverse outcome (mortality). The overall mortality in our study is 12.5%. Mortality in patients with MPI score < 21 was 0%, 21-29 was 4.3% and >29 was 53.84%. This reproducible scoring system allows a surgeon to determine the severity of intra-abdominal infections, to select a more aggressive management for high risk patients and to be able to inform patient's relatives with greater objectivity.