Forty-five patients with chronic pancreatitis (of whom only 14 had pancreatic calculi) were investigated by endoscopic pancreatography and the secretin-pancreozymin test in order to explore the relationship between exocrine function and duct morphology in this disease. Each pancreatogram was assigned a score that ranged from 1 when the duct system was normal to 6 when a chain-of-lakes replaced the main duct; the scores attained were compared with the respective secretory volumes, bicarbonate concentrations, bicarbonate outputs, and trypsin outputs of exocrine secretions. Although a significant negative correlation emerged in each instance, the secretory overlap between the six subgroups was so marked as to render impractical any prospect of accurately predicting the pancreatogram appearance on the basis of prevailing pancreatic function in any individual case, or vice versa. The likely explanation for this result is that (a) chronic pancreatitis is a patchy process in which the acini and ducts are variably affected, and (b) destruction of parenchyma and obstruction to drainage of secretions contribute in varying proportions to the decrease in exocrine function.