Erectile dysfunction is rarely caused by hypogonadism. We distinguish between primary and secondary hypogonadism. Among 70 consecutive men treated for impotence within 1 year in the authors' clinic, the rate of endocrinopathy was 4.3%. The exact role of testosterone in male sexual function is unclear. Testosterone replacement may be helpful only in patients with low serum testosterone and decreased libido. Endocrine screening is necessary in impotent patients with clinical signs of hypogonadism. Patients with decreased libido and no signs of hypogonadism should also be undergo endocrine evaluation. Routine endocrine testing for all patients with erectile dysfunction is expensive and not productive.