The role of reactive oxygen metabolites in extrapancreatic organ dysfunction associated with acute hemorrhagic pancreatitis was studied in dogs. Experimental pancreatitis was induced by the intraductal infusion of activated trypsin and taurocholate. Cardiac output, pulmonary and systemic blood pressure, pulmonary wedge pressure, central venous pressure, heart rate, blood gases and serum amylase were measured. Cardiac index, pulmonary and systemic vascular resistance, and the right and left stroke work were calculated. Systemic arterial and venous blood pressure and cardiac index gradually declined over 6 hr, while pulmonary mean blood pressure and pulmonary vascular resistance increased. Pretreatment of pancreatitis with catalase and superoxide dismutase prevented the rise in mean pulmonary blood pressure, moderated the rise in pulmonary vascular resistance, and decreased the rate and extent of the fall in cardiac index. These data suggest that reactive oxygen metabolites may play some role in the extraabdominal organ manifestations of acute pancreatitis.