The mechanism by which varicocele caused infertility is not yet clear. Endocrine factors have been suggested to explain impaired spermatogenesis in patients with varicocele. We conducted a prospective study on testosterone and gonadotropin levels and their response to the luteinizing hormone-releasing hormone test to determine the possible role of a hormonal defect in subfertility. Luteinizing hormone-releasing hormone tests were performed on 11 subfertile men with varicocele preoperatively and 3 months postoperatively. The differences in the luteinizing hormone response were statistically significant. The maximal luteinizing hormone levels also were significantly lower in patients whose spermiogram changed postoperatively. No significant changes were noted in testosterone and other gonadotropin levels postoperatively. A prognostic correlation between the change in response of luteinizing hormone to luteinizing hormone-releasing hormone (preoperatively and postoperatively) and improvement in fertility (pregnancy success) was found. We suggest that the luteinizing hormone-releasing hormone test should be considered to estimate the hormonal derangement and also the prognosis of an operation in subfertile men with varicocele.