We employed anti-human sperm monoclonal antibodies to investigate how sperm membrane antigens are involved in gamete interactions. We have produced seven monoclonal antibodies specific for human sperm antigens, that showed reaction with mouse sperm by ELISA and by immunofluorescence. These antibodies did not react with zona pellucida or any other somatic human tissue. Some degree of toxicity was detected for oocytes at high antibody concentration and this was correlated with their inhibitory effect on fertilization. Unrelated to the degree of antigen expression or localization on sperm membrane, the antibodies showed several degrees of inhibition. The participation in sperm-zona pellucida interaction for every antigen could be evidenced by the impaired penetration of sperm caused by the presence of several concentrations of antibody. Thus, DAN-2, MOU-8 and VAC-4 inhibit mouse in vitro fertilization. © 1994 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.