Acute hemorrhagic pancreatitis has been produced in dogs by two separate intraarterial injections (20 and 10 micrograms/kg) of venom from the scorpion Buthus quinquestriatus. Morphological changes related to the development of the disease were detectable by electron and light microscopy at 1 and 3 hr, respectively, following the injection of venom. Six hours following venom injection, widespread areas of hemorrhage and fat necrosis were observed on the surface of the pancreas and adjacent mesenteries. By 24 hr, areas of fat necrosis more than 1 cm in diameter were present on the surface of the pancreas. No free protease was found in pure pancreatic juice collected at 3, 6, 24, and 96 hr after the injection of Buthus quinquestriatus venom. Amylase concentrations in serum increased to a maximum sevenfold above the basal level at 6-8 hr after injection. Since acute hemorrhagic pancreatitis occurred both with and without pancreatic duct cannulation, it is likely that the pathological process is independent of any venom effect on papillary sphincter tone. The morphological characteristics of the experimental disease appear similar to those observed at autopsy in acute hemorrhagic pancreatitis in humans.