To test the hypothesis that endotoxin is absorbed from the gut into the circulation in rats with experimental acute pancreatitis we studied two different animal models. In the first model necrotizing pancreatitis was induced by the ligation of the distal bilio-pancreatic duct while in the second, experimental oedematous acute pancreatitis was induced by subcutaneous injections of caerulein. In both experiments, in the colon of rats with acute pancreatitis endotoxin from Salmonella abortus equi was injected. Endotoxin was detected by immunohistochemistry in peripheral organs with specific antibodies. The endotoxin was found only in rats with both acute pancreatitis and endotoxin injected into the colon and not in the control groups. The distribution of endotoxin in liver at 3 and 5 days was predominantly at hepatocytes level around terminal hepatic venules, while in lung a scattered diffuse pattern at the level of alveolar macrophages was identified. A positive staining was observed after 12 hours in the liver, lung, colon and mesenteric lymph nodes of rats with both caerulein pancreatitis and endotoxin injected into the colon. We conclude that the experimental acute pancreatitis leads to early endotoxin translocation from the gut lumen in the intestinal wall and consequent access of gut-derived endotoxin to the mesenteric lymph nodes, liver and lung.