Endocrine function was prospectively evaluated in 98 patients (73 men and 25 women) infected by HIV in various stages of illness: Centers for Disease Control groups II (19), III (20), IVA and IVC2 (27), IVC1 and IVD (32). Testing included baseline and post-stimulation evaluation of gonadal, thyroidal, and adrenal axes. Although adrenal function was within normal values in most cases, with no differences between patient groups, nine out of 98 patients had either a low baseline or post-stimulation serum cortisol, cytomegalovirus adrenalitis being suspected in two cases. Mineralocorticoid response was normal in all individuals. The main abnormalities were sick euthyroid syndrome with low tri-idothyronine and/or thyroxine in 16% of patients and hypotestosteronemia in 29% of men with AIDS. These abnormalities, related to a functional deficiency of the hypothalamic-pituitary axis, were highly correlated with the degree of illness, i.e. weight loss and low CD4+ cell count. It was concluded that endocrine dysfunction in HIV-infected patients is rarely of clinical significance, that it is related more to cachexia and advanced disease than to HIV or opportunistic infections, and that it could serve as a prognostic marker.