We have succeeded in establishing a human monoclonal antibody (MoAb) OC2D against pancreatic cancer cells using lymphocytes from pancreatic cancer patients and a human lymphoblastoid cell line HO323. The reactivity of OC2D using various cell lines and immunoperoxidase staining showed a rather specific effect for malignant cells such as those of pancreatic, gastric, and colon cancers. The antigen recognized by OC2D appeared to be nonsecreting and was mainly found on the cell surface, and various enzyme treatments showed that the epitope was an asialosylated carbohydrate. The hybridoma OC2D has continued to produce human MoAb for 10 months after fusion and grew stably in serum-free medium as well as in serum-containing medium. These results suggest that this human MoAb OC2D is useful for both imaging and targeting therapy.