Serum amylase, lipase and C-reactive protein (CRP) levels upon and CRP again within 72 hours after admission were estimated in 115 consecutive patients with acute pancreatitis and correlated with contrast-enhanced computed tomography (CT) results performed within 72 hours after admission and scored for morphological changes and necroses. Serum enzyme levels > or = 3 times the upper limit of normal and CRP levels > or = 10 times on admission and maximal CRP levels > or = 10 times within 72 hours after admission significantly correlated with severe pancreatic morphological changes. Thus, contrary to previous belief, high, not low, enzyme levels indicate severe acute pancreatitis. Furthermore, maximal CRP levels > or = 10 times the upper limit of normal within 72 hours in all patients and amylase admission levels of > or = 3 times the upper limit of normal in alcoholics were significantly indicative of pancreatic necroses. Thus, serum enzyme estimation upon, and maximal CRP levels within 72 hours after, admission may help the clinician to evaluate the severity of acute pancreatitis when imaging procedures are not immediately available.