These experiments were undertaken as a basic study to develop immunocontraceptive vaccine and to understand the role of zona pellucidae in early fertilization process by investigating the effect of monoclonal and polyclonal antibody to porcine zona pellucidae and polyclonal antibody to mouse zona pellucidae on the fertilization of porcine and mouse eggs in vitro. The results obtained in these experiments were summarized as follows : 1. Treatment of porcine and mouse eggs with undiluted anti-zona serum produced intense precipitation layer on the poricne and mouse zonae, respectively, thus resulting in the total inhibition of sperm adherence on surface of zona. 2. In vitro fertilization of eggs pre-treated with 0.3∼10% of various antibodies was examined, and resulting in that 5 and 10% of rabbit polyclonal antibodies to porcine zona inhibited completely both in vitro fertilization and polyspermy of porcine eggs while monoclonal to porcine zona and rabbit polyclonal antibody to mouse zona did not inhibit in vitro fertilization but monoclonal antibody reduced the rate of polyspermy compared to that of control group. Almost the same results were obtained in the study on the effect of anti-zona serum on in vitro fertilization of mouse eggs.