Starting with a previously established hybridoma producing a monoclonal antibody (F1 alpha 75) against a synthetic glycolipid, in which the carbohydrate moiety was artificially designed to be putatively cancer-specific, we cloned complementary DNA (cDNA) for active variable regions of both heavy and light chains of the antibody. We established a Chinese hamster ovary (CHO) cell line expressing a recombinant F1 alpha 75 of human IgG class. The recombinant F1 alpha 75 retained the binding ability to its antigen and was easily purified. The result suggests that the conversion into the IgG class by genetic engineering is useful for antibodies of the IgM class which are difficult to be purified due to aggregation. Sequence analysis of variable regions of F1 alpha 75 revealed no strong homology with an antibody against galactose, the terminal residue of the synthetic glycolipid, suggesting the clinical usefulness of the recombinant F1 alpha 75.