These experiments were carried out ot detect autoantiboies to zona pellucida in sera from infertile women using indirect ELISA and IFA and to investigate their effect on in vitro fertilization of mouse ova. In inidirect ELISA test, 12 of 116(10.3%) serum samples form infertile women gave positive reaction whereas all of 16 samples from fertile women and men were negative. Furthermore, in indirect IFA test, 17 of 116 (14.7%) serum samples from infertile women gave positive fluorescence whereas all of control sera were negative fluorescence. The fertilization rates(15.9%) of mouse eggs treated with positive sera were significantly lower than those(51.9%＋71.2%) autoantibodies to zonapellucida are responsible for infertility in unexplained infertile women, presumably by perventing sperm attachment and penetration.