Background: Peritonitis is inflammation of peritoneum and peritoneal cavity caused by localized or generalized infection. Primary peritonitis results from bacterial, chlamydial, fungal, or mycobacterial infection in absence of perforation or inflammation of GI or GU tract. Secondary peritonitis occurs in the setting of GI or GU perforation or inflammation with common causes including acute appendicitis, colonic diverticulitis, and pelvic inflammatory disease. Methods: This is an observational prospective cross sectional study including 73 patients presenting to surgical emergency with features of peritonitis. Patient’s information were collected both on hospitalization and after surgical exploration; severity of peritonitis was evaluated using the MPI. According to MPI score patients were divided in appropriate groups(<21,21-27,>27) and analyzed accordingly. The statistical analysis used chi-square test, Kolmogorov-Smirnov test, Kruskal Wallis test& ANOVA test. Result: In groups <21, 21‑27 and > 27 points according to MPI mortality was 0%, 10.53% and 76% respectively. age > 50 was largely associated with increased mortality. There has been a significant correlation between the MPI score and organ failure, Hospital stay. Conclusion: MPI scoring system is a simple and effective tool for assessing this group of patients, and can be used as a guiding tool to decide on the management of the patient after the definitive procedure is done.Increasing scores are associated with poorer prognosis, needs intensive management and hence it should be used routinely in clinical practice