In vitro experiments on fibrin films using purulent exudate from the abdominal cavity of rats with experimental peritonitis demonstrate the fibrinolytic effect of bacterial proteinases immobilized on a polymeric matrix. The application of Imozimaza in the complex treatment of experimental peritonitis by the way of intraperitoneal lavage resulted in reliable lowering of mortality, due to the lysis of fibrinopurulent abdominal contents and better contact between antibacterial agents and peritonitis pathogens. In the clinic, prolonged abdominal proteolysis was applied to 44 patients with postoperative diffuse purulent peritonitis of >24 h duration. Under the conditions of programmable relaparotomy, intraperitoneal Imozimaza infusion led (as in in vitro tests) to the lysis of fibrinopurulent masses, which contained micro-organisms of an order higher than exudate. It was accompanied by increase in the drainage efficacy, absence of fragmentation of abdominal contents and absence of secondary abscesses. The use of Imozimaza on the background of complex antibacterial treatment and combined homeostatic therapy resulted in lowering of mortality from 65.8% to 27.3%. Complications and contra-indications for Imozimaza use in diffuse purulent peritonitis were not registered.