We investigated whether growth hormone(GH) may influence the development of mouse embryo in vitro using recombinant GH and anti-growth hormone receptor(GHR) antibody. When mouse two-cell-stage embryos were cultured with GH, 5, 10 mIU/ml, the rates of formation of both blastocysts and of hatched blastocysts from two-cell-stage embryos were significantly higher than in the medium without GH. The number of blastomeres from blastocyst treated with GH, 2, 5 and 10 mIU/ml, was significantly higher than those cultured without GH. When cultured blastocysts were implanted in recipient uteri, a significantly higher implantation rate was found for the GH-treated(10 mIU/ml) mouse embryos than for controls. To confirm the GH effect, anti-GHR monoclonal antibody MAb5 was employed to neutralize the action of GH through GHR. Two-cell-stage mouse embryos were cultured with GH, 10 mIU/ml, and anti-GHR antibody, and as a control, embryos were cultured with GH alone. Both the rate of formation of blastocysts from two-cell-stage embryos and the number of blastomeres were significantly decreased in groups exposed to anti-GHR antibody. Results indicate that GH may be important to early embryonic development, acting through GHR. GH may help to obtain good quality embryos and improve the implantation rate in IVF programs.