Serum concentrations of trypsinogen-2 and trypsin-2-alpha(1)-antitrypsin (trypsin-2-AAT) were determined in 145 patients with malignant and 61 with benign digestive-tract diseases. The validity of these tests for detection of cancer was compared with that of CA 19-9 and CEA. Elevated levels of trypsinogen-2 (>90 micrograms/l) and trypsin-2-AAT (>25 micrograms/l) were found in 46% and 42%, respectively, of patients with malignant disease and the levels of trypsinogen-2 were significantly higher than in those with benign disease (p<0.005). High trypsinogen-2 and trypsin-2-AAT concentrations were found most often in patients with biliary and pancreatic cancer, but also in benign obstructive biliary disease. Our results suggest that trypsinogen-2 and trypsin-2-AAT are new potential markers for cholangiocarcinomas.