The authors studied the relationship between aging and exocrine pancreatic function by the secretin test which was recently standardized by the Japanese Society of Gastroenterology. Pancreatic juice was collected at 10 min intervals for 60 minutes after a bolus intravenous injection of secretin (Secrepan, Eisai Co., Ltd., 100 U/body) through a quadruple-lumen doudenal tube equipped with double balloons. Exocrine pancreatic function was evaluated by three parameters: secretory volume, maximal bicarbonate concentration or bicarbonate output, and enzyme (amylase and lipase) output. Control subjects consisted of 65 outpatients presenting with mild vague abdominal symptoms who fulfilled the following three criteria: 1) good general condition with no known diseases; 2) no abnormality in the liver, bile duct, pancreas, kidney and metabolism judged from blood chemistry, urine and stool analysis, upper GI series, abdominal ultrasonography (US), and endoscopic retrograde cholangiopancreatography (ERCP); 3) alcohol consumption less than 25 g/day. Control subjects were divided into three groups: 15 subjects below 40 years of age (group A), 32 subjects from 40 to 65 years (group B), and 18 subjects of 65 years and above (group C). Nineteen patient with chronic pancreatitis were also studied. The group C showed significantly lower values in secretory volume, bicarbonate output, and enzyme output than group A and B. Enzyme output showed a gradual decrease with aging. However, secretory volume and bicarbonate output showed a gentle convex curve with a peak around age 40 and a rather steep down-slope after late 50s. The degree of the decrease was significantly more marked in volume and bicarbonate output than in enzyme output in group C.(ABSTRACT TRUNCATED AT 250 WORDS)