Three pancreatic cancer-associated antigens were characterized by use of monoclonal antibodies in immunobinding studies with various cellular and soluble target antigens, in immunoprecipitation, and in immunoperoxidase staining. C54-0 represents a tumor-associated M_r 122,000 antigen, which appears to be widely distributed on various epithelial tumors and to a lower extent on normal tissue. C1-N3 antigen exhibited a more restricted distribution, reacting with pancreatic and various gastrointestinal tract tumors as well as with chronically inflamed pancreatic tissue. The most specific antigen expression was observed for C1-P83 antigen, found on all exocrine tumors of the pancreas, but not on normal or chronically inflamed pancreatic tissue.