Background:Peritonitis is defined as inflammation of the serosal membrane that lines the abdominal cavity and the organs contained therein. Peritonitis as an important entity,is actively associated with acute abdominal catastrophes . Despite advances in surgical techniques, antimicrobial therapy and intensive care support, management of peritonitis continues to be highly demanding, difficult and complex. Methods: A retrospective study was carried out in tertiary teaching care hospital Dehradun,Uttarakhand to evaluate the various prognostic factors in cases of acute generalised peritonitis. Results: A total of 50 cases were included in the study. Maximum incidence of peritonitis was found in 21to 30 years age group. There was male predominance (male to female ratio was 4:1).The causes of peritonitis in order of frequency were duodenal ulcer perforation (32%),traumatic abdominal injury (16%),appendicular perforation (14%),ileal perforation(10%), large gut perforation(6%).Pain was the leading symptom found in 94.6% of cases followed by abdominal distension (80%). The positive culture from peritoneal fluid was noted in 80% of the patients .E.coli was the commonest infecting organism (74%) followed in order of frequency by ps pyocyneus (18%), staph aureus (16%). The overall mortality in acute generalized peritonitis was 28%. The highest mortality was recorded in the seventh decade of life .Timing of surgical intervention within 24 hours gave better prognosis. APACHE II score is effective in identifying the group of patients at risk and to predict death. The Mannhein Peritonitis Index (MPI) has been shown to provide accurate assessment of the severity of peritonitis in these patients. Conclusions: Prognosis in acute generalized peritonitis can be improved by early detection of certain risk factors and instituting early and prompt treatment thereby reducing the incidence of high mortality