A comprehensive evaluation of impotence includes assessment of the functional integrity of the hypothalamic-pituitary-gonadal axis. However, little is known about the incidence or significance of hormonal abnormalities in an unselected group of men with erectile failure. A systematic multidisciplinary, multidimensional assessment of 256 impotent men showed clearly an organic etiology in 35.9 per cent, psychogenic in 38.3 per cent and mixed or uncertain in 25.8 per cent. The incidence of hypothalamic-pituitary-gonadal axis abnormalities in the entire group was 17.5 per cent but in only 12.1 per cent did they contribute clearly to erectile dysfunction. A cost-effective screening of the endocrine system in impotent men includes a thorough history and physical examination, and a serum testosterone determination. More sophisticated and expensive investigations should be reserved for patients with a history of drug use known to induce hormonal abnormalities or with somatic evidence of hypogonadism and a depressed serum testosterone level.