An increased level of antisperm antibodies has been demonstrated in infertile men with varicocele compared with normal fertile men, suggesting a possible cause and effect relationship. To evaluate the possible etiological role of antisperm antibodies in varicocele patients, we performed a prospective study of 32 infertile men undergoing varicocele ligation. Semen analyses and antisperm antibodies as measured by the immunobead test were performed preoperatively and postoperatively at 3 and 6 months. Of the infertile men with varicocele 28% had a positive immunobead test compared with 0% of normal fertile men. The average total motile sperm count was significantly different (p < 0.05, 2-tailed t test) for 9 varicocele patients with sperm-bound antibody (3.2 x 10(6)) compared with 23 without antibody (8.4 x 10(6)). Postoperatively, 68% of all patients exhibited improved semen parameters, with no change in antibody status in either group. Among the antibody positive group 71% showed an increase in motile sperm per ml. of 2.8 x 10(6) to 17.2 x 10(6) (525% increase, p < 0.05), while in the antibody negative group 67% showed an increase of 3.8 x 10(6) to 24.9 x 10(6) (553% increase, p < 0.05). Our study suggests that there is an increased incidence of sperm-bound immunoglobulin in infertile varicocele patients and an apparent adverse effect on semen parameters in these patients. However, the presence of sperm-bound immunoglobulin did not affect the percentage response to surgical correction, nor can we postulate an immunological mechanism as a major etiological factor in varicocele induced infertility.