These experiments were carried out to investigate of the molecular characteristics of porcine zona pellucidae and to examine the reactivity of anti-zona antibody by SDS-PAGE, Immunoblotting and Immunoprecipitation. The results obtained in these experiments were summarized as follows : 1. The result obtained by SDS-PAGE of porcine zona pellucidae indicated that it composed of several units with molecular weight ranging 55,000-110,000. 2. In order to see the reactivity of antibodies to zona pellucidas, immunoblotting was applied. The results indicated that polyclonal antibodies to porcine and mouse zona reacted with porcine zona. While monoclonal antibody to porcine did not react with the procine zona enough to show a clear band on a gel. 3. Labelling of porcine zonae with 125I was performed using the Iodogen method, the radioactivity and the percent incorporation of 125I into porcine zonae were approximately 26,000 cpm/10${mu}ell$ and 16, respectively. 4. Measurements of radioactivity and O.D value for Immunoprecipitates produced by reaction of 125I-porcine zona with anti-zona antisera were confirmed that existence of reactivity of monoclonal antibody to porcine zona although its reactivity was lower than that of polyclonal antibodies, and reconfirmed that cross-reactivity of polyclonal antibody of mouse zona with porcine zona.