Acute pancreatitis of biliary tract origin and that of alcoholic origin may be difficult to separate on clinical grounds alone. Such separation is important since operation prevents recurrent attacks in gallstone pancreatitis. We examined the records of 78 patients in the first attack of pancreatitis from gallstones or alcohol. The gallstone group were usually women, older, and had a shorter period of abdominal pain. Pancreatic complications occurred more frequently in the alcoholic group and led to two deaths. Amylase values were diagnostically helpful in that a level greater than 1000 units in patients of the proper age and sex, and a level greater than 2000 units by itself indicated gallstone pancreatitis.