Although varicocele remains the most frequently diagnosed cause of male infertility, and improvement in semen quality is associated with repair of varicocele, improvement in spermatozoal fertilizing capacity has not been conclusively demonstrated. The sperm penetration assay was employed to monitor prospectively surgical (n = 59) and nonsurgical (n = 40) groups of men with varicocele. There were no significant increases in the average count, motility, morphologic features, or sperm penetration assay results for either group. Varicocele surgery enhanced assayable egg penetration rates in 14 of the 59 patients (23.7%), whereas the nonsurgical group had 10% spontaneous improvement. Of those in the surgery group who showed assayable fertility enhancement and were attempting conception, pregnancies were achieved in 70% (7 of 10 patients). Of patients in the nonsurgical group who improved in the assay, no pregnancies were obtained.