Pancreatic secretory function is abnormal in at least 90% of patients with pancreatic cancer. These abnormalities may be due to direct involvement of the secretory cells by the malignant process and/or the effects of pancreatic duct obstruction. There is no specific stimulus (secretin and/or cholecystokinin, CCK, or CCK-like hormones) of pancreatic secretion that is clearly superior to any other as a test of pancreatic function. Pancreatic secretion is abnormal in animal models of pancreatic cancer and secretory abnormalities antedate the histologic appearance of the cancer. A decrease in protein secretion after CCK stimulation is the most significant finding in experimental partial pancreatic duct obstruction (the condition most commonly seen in pancreatic cancer). In the absence of any identifiable high-risk group within the population, it is unlikely that the testing of pancreatic function provides a means for the earlier diagnosis of pancreatic cancer.