Seventy-two couples, including 15 with antispermatozoal antibodies in the male partner's semen, were studied in a program of in vitro fertilization and embryo transfer. Cases were further subclassified as normospermic or oligospermic and antispermatozoal antibodies were assessed with categorization into the respective human immunoglobulin classes as determined using the indirect immunobead test. The study reveals that fertilization is significantly reduced (P less than 0.001) only if both IgA and IgG antibodies are present in semen but there is no reduction if either class is present alone. The fertilization rate of oocytes is significantly reduced (P less than 0.001) by sperm from oligospermic samples, and there is a further reduction in those cases with combined IgA/IgG antispermatozoal antibodies.