[en] An immunoradiometric assay (IRMA) for human chorionic gonadotropin (HCG) in serum is established based on two monoclonal antibodies against HCG. there are no cross-reaction with human luteinizing hormone (hLH), follicle stimulating hormone (hFSH) and thyroid stimulating hormone (hTSH). The sensitivity was 0.5 U/L, and the recovery for different concentration of HCG was 91.65%-107.62%. The coefficients of variation for intra and inter-assay were less than 5.4% and 6.4% respectively. ¹²⁵I-McAb were stable under the storage of 4 degree C for 97 days