To evaluate the prevalence of antisperm antibodies (ASA) attached to the sperm plasma membrane in male partners of infertile couples, the binding of latex particles to spermatozoa was investigated using SpermMARtest, included routinely in semen analysis. A total of 860 men were examined, who were referred consecutively for semen analysis. Of these, 750 men were referred because of infertility (0.6-10 years in duration) whereas 110 were volunteers with a history of previous fertility. Samples were assessed by the SpermMARtest kit using latex particles sensitized with human IgG. Sperm-latex binding was read after 3 min and samples scored as negative, positive or highly positive when < 10, > 10-40, or > 40% binding occurred, respectively. Of the samples 132 (17.3%) were excluded because of azoo- or severe oligo-asthenozoospermia. IgG attached to spermatozoa were detected in nearly 13% of semen samples from the infertile population and in one of 110 fertile men (0.9%). From the infertile group, 6.2% of samples showed > 40% binding, and 6.7% intermediate binding, with an overall ASA prevalence of 12.9% in subjects undergoing semen analysis for infertility.