During acute pancreatitis, data obtained in vitro suggest that pancreatic lipase, acting on circulating or tissular triglycerides, might generate nonesterified fatty acids (NEFA) that could promote pancreatic and fat tissue necrosis. This work determined whether NEFA were actually produced in vivo in pancreatic tissue and in blood during cerulein-induced pancreatitis in rats. Intraperitoneal injections of cerulein induced pancreatitis. To promote the possible NEFA release by pancreatic lipase, a venous infusion of human very low density lipoprotein (VLDL) was used to cause hypertriglyceridemia. NEFA were measured in portal and aortic blood and in tissue extracts prepared from pancreas homogenates. NEFA did not increase either in peripheral or in portal blood. In pancreatic tissue, NEFA levels did not differ from controls. The major hypertriglyceridemia produced by human VLDL intravenous infusion neither altered the course of the disease nor promoted plasma NEFA release. The role commonly attributed to NEFA in acute pancreatitis seems questionable.