Pure subunits of human chorionic gonadotropin (hCG) were obtained by chromatographic separation using DEAE-Sephadex A-25 and Sephadex G-75 for the immunization. The spleen cells obtained after immunization of either w-hCG or β-subunits were fused with myeloma cells and twelve hybridoma cell lines were established. The results showed that the fusion efficiency and antibody producibility varied depending on the myeloma cell lines. The cell line P3×63-Ag8.653 was found to be a better fusion partner than SP2/0 for the production of antibodies from hybridoma cells. For the formation of ascitic fluid in mice, Incomplete Freund`s Adjuvant(IFA) was a better priming agent than pristane. The yield of specific monoclonal antibodies by the immuno-affinity purification method was 1.6-3.4 ㎎/㎖ ascitic fluid. Seven clones were studied for the specificity to w-hCG and its subunits using ^(125)I-labeled tracer and the clones were classified into 3 groups. The equilibrium affinity constants of the seven antibodies ranged from 5×10^7 M^(-1) to 8×10^8 M^(-1).