Acute pancreatitis caused by Ascaris lumbricoides is more common in certain areas than is generally appreciated. We report a series of 42 patients, mostly young adult women, admitted to our hospital in Hunan Province, China, during the period January, 1983 to December, 1992. The diagnosis was based on the detection of worms by ultrasonography, and on the presence of severe upper abdominal pain and tenderness and raised serum amylase level without other apparent causes. Only 2 patients had necrotizing pancreatitis (4.8%). With our conservative policy, 40 patients recovered and 2 patients were operated. The mortality has remained at zero and we therefore believe that early surgical intervention is unwise. However, laparotomy should be performed if the patient fails to respond to conservative therapy, there is evidence of infection around the pancreas, bloody peritoneal fluid on aspiration, and dead worms remain within the biliary tree. We compare acute ascaris pancreatitis with acute pancreatitis caused by lithiasis.