There have been many reports on aging of the pancreas; decrease in weight, atrophy and fatty degeneration of the acinal cells, increase of the interacinar connective tissue, arteriosclerosis and so on. However, only a limited number of reports have been published on changes in the exocrine pancreatic function as related to aging and these results are controversial. Furthermore reports on morphological changes of the pancreas, especially of the pancreatic duct, have been limited to a small number of studies with histological evaluation. The purpose of the present study is to elucidate morphological as well as functional changes of the aging pancreas in the light of recent developments in thinking of: (1) functional changes of the exocrine pancreas as evaluated with the pancreozymin-secretin test; (2) morphological changes of the pancreatic duct as evaluated with endoscopic retrograde cholangiopancreatography; (3) correlation between functional and morphological changes. The present paper is concerned with studies on changes of the exocrine function of the aging pancreas as evaluated with the panceozymin-secretin test according to the modified Sun-Shay method. The material was taken from healthy controls accommodated in an old-age home, healthy controls hospitalized for routine annual check-ups, and patients who had no abdominal or metabolic disease. The 60 controls were subdivided into three groups according to age for comparative studies: 21 to 40 years of age; 41 to 60 years of age; older than 60 years of age. The following conclusions were made: (1) A significant decrease in the exocrine pancreatic function was observed with aging. (2) The decrease of exocrine pancreatic function with aging was unrelated to the body weight of controls, the doses of pancreozymin and secretin determined according to the body weight, sex, or the history of alcohol ingestion in cases where daily intake was limited to less than 33 g of ethanol. (3) Because of the decrease in exocrine pancreatic function, physiological ranges of secretory volume, maximal bicarbonate concentration, bicarbonate output and amylase output on the pancreozymin-secretin test were determined for each age group.