The purpose of hormonal testing in infertile men is to screen treatable causes of infertility. Recommendations of the American Urological Association and the Society of Reproductive Medicine are to measure serum follicle-stimulating hormone (FSH) and testosterone if there is an abnormally low sperm concentration, impaired sexual function or clinical findings suggestive of endocrinopathy. If testosterone level is low, measurement of total and free or bioavaible testosterone should be performed as well as determination of luteinizing hormone (LH) and prolactin level. This hormonal evaluation can distinguish hypogonadotropic hypogonadism from testicular insufficiency.