ABSTRACT: The aims of this investigation were to determine the incidence of sperm-bound antibodies in an unselected infertile population and also to further evaluate the immunobead test (IBT) with respect to specificity and reproducibility. The results of the survey showed that 7.8% of 813 men had antibodies of IgG and/ or IgA class bound to the surface of at least 20% of their motile spermatozoa. The results of crossed-inhibition tests with purified human immunoglobulins and comparison of the IBT results with the sperm-immobilization test (SIT) in serum and sperm agglutination in semen suggested that the IBT is an immunologically specific test for sperm antibodies. Comparison of repeat tests on 123 patients showed that the IBT is reproducible in 97.5% of cases. There was no difference in mean count, percentage motile, or morphology between the groups of patients with positive or negative IBT results. The incidence of sperm agglutination was significantly (Chi-squared, p < 0.001) higher in the positive IBT group. The results of this investigation therefore suggest that the IBT is an excellent test for routine screening of men for sperm antibodies.