This experiment was carried out to develop a new technique of identifying XX of XY-bearing bisected embryos prior to implantation by immunological method. H-Y antiserum prepared in inbred Wastar female rats by repeated immunization with spleen cells from males of the same strain. The reactivity of H-Y antibody was confirmed by culturing mouse embryos in the medium containing H-Y antiserum and complement obtained from the guinea pig. The optimal condition for the activity of H-Y antibody was also investigated by culturing embryos under the concentraton or affected H-Y antibody was also investigated by culturing embryos under the concentration or affected H-Y antibody and culture rate. However, production of live young or sex rates of male and female from embryos transferred with psudopregnant. The biological test with the morula stage embryos showed that H-Y antibody was formed in all female rats immunized with spleen cell, but it was formed only in 80% female rats immunized with the antigen. When the bisected mouse embryos were cultured in vitro for 5~6 hours in morula stage, of 457 bisected embryos 81.4% of then were developed to the blastocyst stage. When the concentration rate of complement to H-Y antiserum varied from 1.0~5.0${mu}ell$, the lysis-rate of embryo was 19.5 to 67.3%. The concentration rate of complement did not influence the lysis-rate of embryos(P<0.05). The morphology embryos of bisected, zona-free and intact embryos showed the embryos lysis rate of 58.6, 42.7 and 48.5% respectively(P<0.05). Pregnancy rate were 50.0, 45.5 and 57.1% in psudopregnant recipient transferred with bisected, zona-free and intact blastocyst embryos. However, production of live youngs, sexual rate of male or female was 24(50.0:50.0), 22(45.5:55.5) and 36(58.3:41.7)mice, but affected and non affected half embryos with H-Y antiserum treatment was 23.1 and 26.7%. Also production of live youngs and sexual rate was 14(92.9:7.1) and 17(17.6:82.4)mice in affected and non affected half embryos in H-Y antiserum treatment(P<0.05).