Acute pancreatitis was induced in 13 anesthetized dogs by retrograde injection of bile mixed with trypsin into the pancreatic duct. Six animals were treated with intravenous infusion of new synthetic antiprotease. Nafamostat Mesilate, at a dose of 1 mg/kg/h. Four out of seven untreated animals died during the experiment. All the treated dogs survived. Hemodynamic data were regularly monitored during a ten-hour observation period. Cardiac output, mean arterial pressure and left ventricular stroke volume decreased rapidly in the untreated animals. An increase in systemic vascular resistance and pulmonary vascular resistance was observed in dogs without treatment. Nafamostat Mesilate given as therapy significantly improved the hemodynamic parameters, and prevented the animals from developing shock. The study demonstrates an advantageous influence of synthetic antiprotease Nafamostat Mesilate on the course of acute experimental pancreatitis.