[en] We investigated the biodistribution, radiolocalization, and radioimmunotherapeutic potential of ¹³¹I-labeled Nd2 in athymic nude mice bearing human pancreatic carcinoma xenografts. ¹³¹I-Nd2 was accumulated at high levels in the tumor, in contrast to blood, liver, spleen, and other normal organs. The tumor was clearly delineated in scintigraphs. The volumes of tumors of mice injected with 7.4 MBq of ¹³¹I-Nd2 were 80% less than those of tumors before injection of radiolabeled Nd2. Fibrous or vacuolar degeneration was seen in histological sections of tumors of 7-week-treated mice. The growth of tumors in mice treated with misonidazole, a hypoxic cell radiosensitizer, and then injected twice with 3.7 MBq of ¹³¹I-Nd2 was suppressed over 7 weeks. Neither leucocytopenia nor thrombocytopenia was severe after injection of radiolabeled Nd2. Thus ¹³¹I-labeled Nd2 may have clinical application in the radioimmunotherapy of pancreatic cancer. (author)