A previous report has shown that undernutrition reduces the mortality of acute experimental pancreatitis probably by decreasing pancreatic enzyme content. Cerulein in physiological doses reduces the enzyme content of the pancreas without any harmful effect on the organ. The aim of the present study was to asses the effect of acute reduction of pancreatic enzyme content on the outcome of acute pancreatitis. Two groups of male Wistar rats weighing 230-250 g were studied: group I, 12-h fasted animals, and group II, ad libitum-fed animals who received cerulein at the inframaximal dose (0.2 microgram kg-1 h-1) for 2 h. Cerulein administration resulted in the reduction of the pancreatic contents of chymotrypsinogen (71%), trypsinogen (55%), proelastase (60%), amylase (62%) and cathepsin B (45%) (P < 0.05). However, no significant reduction in pancreatic phospholipase content was observed. Acute pancreatitis was induced in group I after 12-h fasting and in group II at the end of cerulein infusion by retrograde injection o 0.5 ml of 2.5% Na+ taurocholate into the pancreatic duct. Ascites volume and the degree of histologically observed lesions were similar in both groups, but 72-h mortality was 56% in the control group (10/ 18) and 23% (5/22) in the cerulein group (P < 0.05). We speculate that the reduction of pancreatic enzyme content may exert its beneficial effect in acute pancreatitis by decreasing the quantity of pancreatic enzymes reaching the circulation and consequently their pathogenic effects.