Encouraged by reports of radioimmunoimaging of colorectal carcinomas and by examining an immunohistochemical report on resected pancreas cancer tissues, we studied the diagnostic potential of radioimmunoimaging with the radioiodinelabeled monoclonal antibody to the surface antigen of a pancreas cancer cell line. A monoclonal antibody (MoAb; HC-1) to a human pancreas cancer cell line (HGC25)5 was labeled with radioiodine and injected into athymic nude mice implanted with human pancreas cancer cells. Antibody HC-1 was cleared from the circulation and accumulated significantly in the implanted tumor sites.