The CT findings in 28 patients with acute pancreatitis were compared with the severity of the disease. The pancreatic image, which demonstrates the pancreatic lesion, was studied with respect to 9 items, and fluid accumulation showing the peripancreatic status with respect to 13 items. According to Forell's classification, the lesion was mild in 8 patients, moderate in 11, and severe in 9. The detection rates of abnormal pancreatic images and fluid accumulation increase with the advance in the severity of the disease. The mean CT score according to severity was 0.9 +/- 0.6 for mild pancreatitis, 7.2 +/- 4.5 for moderate pancreatitis, and 13.4 +/- 4.2 for severe pancreatitis. Significant differences were observed among the groups, suggesting that the CT score is useful for evaluating the severity of acute pancreatitis.