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The immunoscintigraphic results in 12 human pancreatic carcinomas established on nude mice (Nu-Nu-Balb-C) are reported. The transplanted tumors corresponded to the human cancers concerning histology, grading, immunohistochemistry and secretion of tumor-associated antigens. 131I-labeled monoclonal antibodies against CA 19-9, CEA and CA 125 were used. These antigens are found in the serum of more than 90% of patients with pancreatic carcinoma at the time of first diagnosis. The result show that pancreatic carcinomas are detectable with the antibodies applied here. The quality of the scintigraphic detection depends, among other factors, on the antibody affinity to the tumor, the localization and the size of the tumor. Preliminary results of the studies on radioimmunotherapy of pancreatic cancer with 131I-anti-CA 19-9 indicate that effective absorbed doses in the tumor may be achieved via intravenous application only in cases with a rather high expression of the tumor antigen. But direct instillation into the tumor enables therapeutic radiation doses to the tumor even with moderate affinity and a low whole-body burden, as shown by experiments in 8 mice bearing 4 different human pancreatic carcinomas, 3 with positive and 1 with negative affinity to CA 19-9: the tumor retentions and the effective half-lives of 131I-anti-CA 19-9 were measured after intratumoral (100 microCi/mg tumor) or intravenous (30 and 190 microCi/g body weight) application.