Five patients with severe acute pancreatitis had a low contrast enhancement (CE) of the pancreas in computed tomography (CT) and underwent subtotal pancreatectomy. Microangiography and histologic studies were performed on the resected pancreases, and the findings were related to those of CE. All patients had histologically documented hemorrhagic/necrotizing pancreatitis. The more disturbed the vascular anatomy in microangiography, the more hemorrhages and necroses were found in histology. The microangiographic and histologic findings corresponded closely to the low contrast-enhanced CT of the diseased pancreas in each patient. Thus, in the early phase of severe acute pancreatitis, one can detect by noninvasive means which areas of the gland are necrotic and which edematous by a dynamic study of contrast-enhanced CT of the pancreas.