Recently, endotoxaemia has been reported as a prognostic marker in acute pancreatitis. However, the role of endotoxin in inducing or aggravating acute pancreatitis is not fully understood. We administered endotoxin 400 micrograms/kg i.p. to rats 24 h before performing either a closed duodenal loop (group B) or a sham operation (group D). Pancreatic damage and overall survival were compared with the results obtained in rats not exposed to endotoxin undergoing either closed duodenal loop (group A) or sham treatment (group C). In a first set of experiments, 24 h after laparotomy blood samples were collected and the animals were sacrificed; survival up to 8 days was estimated in a second set of experiments. Group B had higher lipase concentrations and more severe tissue damage than group C (P < 0.05). A larger number of abscesses was observed in both group B and group D as compared to group C (P < 0.05). Survival was significantly shorter in group B (P < 0.0001). We conclude that priming with endotoxin worsens the extent of pancreatic damage induced by the closed duodenal loop procedure in the rat, possibly favouring selective homing of neutrophils to the site of inflammation, in similarity to what happens in the Shwartzman phenomenon.