It has been found that the presence of a high number of leukocytes and the presence of lung alterations may identify those patients with severe acute pancreatitis [5]; in fact, using a cut-off value of 13,000/mm3, 45% of patients with severe pancreatitis and 17% of those with mild acute pancreatitis had a peripheral leukocyte count greater than 13,000/mm3. Pleural or pulmonary alterations observed on chest X-ray were found in 66% of patients with severe pancreatitis and in 2% of those with mild acute pancreatitis. A peripheral leukocyte count greater than 13,000/mm3 and/or pleural or pulmonary alterations present on chest X-ray were found in 78% of the patients with severe pancreatitis and in 19% of those with mild pancreatitis. Pulmonary leukocyte infiltration measured by technetium-99mlabelled leucocytes demonstrates that leucocytes in the lungs are increased in animals with both moderate pancreatitis and severe pancreatitis induced by the intraductal infusion of glycodeoxycholic acid while moderate alterations were noted in animals with mild pancreatitis induced by intra-arterial infusion of cerulein [6]. In rats with experimental necrotizing pancreatitis induced by the intraductal administration of sodium taurocholate [7], significant pulmonary edema, hyperemia and inflammatory infiltrates, predominantly composed of polymorphonuclear leucocytes in the alveoli, were noted 12 h after the induction of pancreatitis, accompanied by an increase in the levels of the arachidonic acid metabolites. Transport of carbon dioxide through the alveolar barrier was significantly compromised due to increased interstitial edema and type I pneumocyte dysfunction or the existence of arteriovenous shunting in the lungs as well as in other tissues [8]. The activated alveolar macrophages were characterized by an increase in the generation of nitric oxide, tumor necrosis factor (TNF-alfa) and macrophage inhibitor protein 2. Most importantly, the instillation of supernatants from activated alveolar macrophages harvested from pancreatitis animals caused neutrophil sequestration in normal animals [9], implying that the activation of lung