The duodenal aspirates were analyzed for amylase, lipase, trypsin and chymotrypsin contents in healthy patients and in subjects with chronic pancreatitis and pancreatic carcinoma. The duodenal aspirate was obtained in basal conditions and under continuous infusion of 3 U/kg/h of cholecystokinin (GIH). Lipase exhibited the largest increase under cholecystokinin stimulation and the smallest variation coefficient and degree of overlap between control subjects and patients with abnormal pancreas. healthy subjects, cholecystokinin stimulation induced significant deviations from parallelism for the enzyme ratios involving lipase. Such deviations tendedto disappear in patients with pancreatic disease.