Information from 72 patients from 7 families in England and Wales confirms that hereditary pancreatitis is inherited as an autosomal dominant conditions with limited penetrance. The degree of penetrance is approximately 80%. These patients have had recurrent attacks of abdominal pain starting from childhood or young adult life. The mean age of onset in the 7 families studied was 13.6 years. There were two peaks, with maximum numbers at 5 years and 17 years. The second peak was thought to represent genetically susceptible individuals having pain brought on by alcohol rather than representing evidence of genetic heterogeneity. Five of the 7 families had members with both childhood and adult ages of onset. Only 4 patients out of 72 had life-threatening disease and in the majority of cases the attacks of pain were of nuisance value only. Hereditary pancreatitis was implicated in only 1 patient's death and this was not definite. Patients appear to get better after a period of symptoms usually as they approach middle age, or after a severe attack. In older patients alcohol, emotional upsets, and fatty food appear to precipitate attacks. Pancreatic insufficiency (5.5%), diabetes mellitus (12.5%), pseudocysts (5.5%), and haemorrhagic pleural effusion are uncommon complications. Portal vein thrombosis occurred definitely in 2 patients and was suspected in 3 others. Carcinoma of the pancreas was not found in any of 72 patients studied in detail; however, 2 members from a family not visited personally had chronic pancreatitis and malabsorption going on to carcinoma. They may have suffered from a different disease. Genetic linkage information was too slight for many definite conclusions. However, there was no suggestion of linkage with any of the markers tested.