Clinical features of adrenal steroid deficiency occur in patients with the acquired immunodeficiency syndrome (AIDS). To determine the frequency of aberrations in peripheral steroid levels in patients with AIDS and AIDS-related complex (ARC) we measured morning recumbent plasma cortisol, deoxycorticosterone, 18-hydroxydeoxycorticosterone (18-OHDOC), corticosterone, aldosterone, and 18-hydroxycorticosterone concentrations before and after administration of 0.25 mg ACTH (Cosyntropin) in 74 randomly selected hospitalized patients with AIDS and 19 patients with ARC. Basal (0800 h) cortisol levels in the AIDS patients were significantly higher (P less than 0.01) than those in normal subjects, while other ACTH-dependent steroids of the 17-deoxypathway, deoxycorticosterone, corticosterone, and 18-OHDOC, were normal. These latter steroids increased subnormally in response to ACTH in patients with either AIDS (P less than 0.001) or ARC (P less than 0.005), but in ARC patients plasma 18-OHDOC levels were significantly higher than in those with AIDS (P less than 0.001). Supraphysiological doses of ACTH were then administered for 3 consecutive days to 14 patients with AIDS and 9 with ARC, which confirmed and amplified the subnormal responses of these steroids in AIDS. The mean plasma cortisol response was reduced on the third day only in AIDS patients, whereas in the ARC patients the steroid responses were normal. Angiotensin III infusion and postural stimulation increased plasma aldosterone and 18-hydroxycorticosterone levels in AIDS and ARC patients. Defective stimulation of 18-OHDOC alone or in combination with defective stimulation of other 17-deoxysteroids can be a harbinger of subsequent impaired adrenal capacity in AIDS.