Varicose veins in the scrotum (varicocele) are responsible for >20% of male infertility in the US. Varicocele are associated with decreased sperm number and markedly reduced sperm fertilizing ability. Surgical repair or removal of varicocele restores fertility in only 1/3 of cases. The goal of this study is to identify markers that predict the outcome of variocele correction. This would offer considerable health cost savings.