We have studied a 32-year-old patient who was infertile because of azoospermia, We made the final diagnosis of non-classical congenital adrenal hyperplasia (CAH) caused by 21-hydroxylase deficiency with adrenal rest tumor of bilateral testes and bilateral adrenal myelolipoma. The patient was given 1.5 mg/day dexamethasone. Decreases in the levels of 17 OHP and adrenal androgen were rapidly observed. After 5 months of treatment, semen analysis showed a sperm density of 2 x 10(4)/ml with 50% motile spermatozoa. His wife became pregnant and delivered of a healthy daughter. We conclude that chronic suppression of gonadotropins secretion caused by overproduction of adrenal androgens in CAH would appear to be the cause for the failure of testicular development and spermatogenesis.