Infertility is due to a significant male factor alone, whereas combined male and female factors are present in an additional 20%. Thus, a male factor is involved in approximately 50% of infertile relationships. The primary goals of the evaluation of the male presenting with infertility are to identify: etiologic conditions, irreversible conditions, irreversible conditions not amenable to assisted reproductive techniques, medically significant pathologies, and genetic etiologies. Bilateral cryptorchidism results in a significant decrease in spermatogenesis, while the effect of unilateral cryptorchidism appears to be much milder. Approximately 50% of testicular cancer patients have subnormal sperm densities prior to chemotherapy. Of note, of those with oligo- or azoospermia, 75% normalized during surveillance. Diethylstilbestrol (DES) was given to pregnant women in the 1950s, and reports of epididymal cysts and cryptorchidism in males with prenatal DES exposure have raised concerns about effects on fertility. Exogenous androgens are well known to induce hypogonadotropic hypogonadism.