Comparative studies of DU-PAN-2, carcinoembryonic antigen, and CA19-9 in the serum and bile of patients with pancreatic and biliary tract diseases: evaluation of the influence of obstructive jaundice. The levels of DU-PAN-2 antigen, carcinoembryonic antigen, and CA19-9 in serum and bile of patients with pancreatic and biliary tract diseases were measured. The sensitivities (true positive) of DU-PAN-2 in serum to pancreatic carcinoma (64%) and to biliary tract carcinoma (62%) were similar to those of CA19-9 in serum (69% and 72%, respectively). Nine of 18 (50%) patients with CA19-9-negative pancreatic carcinoma tested positive for DU-PAN-2. The sensitivities of CEA to pancreatic carcinoma (56%) and to biliary tract carcinoma (52%) were lowest. The measurement of these antigens in bile seemed to be of little diagnostic value in differentiating between malignant and benign diseases. False positives of these three assays occurred frequently in patients with benign pancreatic or biliary tract disease coupled with obstructive jaundice. After percutaneous transhepatic biliary drainage, serum DU-PAN-2 and CA19-9 levels returned to normal ranges in patients with benign diseases, but not in patients with carcinoma of the pancreas or of the biliary tract. Serum CA19-9 and DU-PAN-2 antigens are useful tumor markers for pancreatic and biliary tract carcinomas. Longitudinal assays of these antigens may be useful for the differential diagnosis of patients with obstructive jaundice. 