Antisperm antibodies are significant in male factor infertility. The prevalence ofantisperm antibodies in the infertile population is approximately 10 percent, and it is not cost-effective to test for these antibodies in every male partner of an infertile marriage. Earlier studies have demonstrated a higher prevalence of antisperm antibodies among men with a history of bacterial prostatitis or urethritis. Because of this established association, we measured the prevalence of serum antisperm antibodies, using a gel agglutination assay, in 28 men with chronic nonbacterial prostatitis and in an age-matched control group of 69 men without a history of prostatitis. The prevalence was 25 percent (test subjects) and 7.2 percent (controls) (p < 0.05). This finding indicates that nonbacterial prostatitis is a risk factor for the presence of serum antisperm antibodies and that subfertile men with a history of nonbacterial prostatitis should be tested for these antibodies. © 1990 Cahners Publishing Company, A division of Reed Publishing USA.