The hippocampus is a major center for the regulation of the hypo-thalamic-pituitary-adrenal axis. There is experimental evidence that chronic exposure to high levels of glucocorticoids may be toxic to the hippocampus. We observed elevated mean basal and 60-min cortisol (F) levels in response to adrenocorticotropin stimulation (0.25 mg cortrosyn, i.v. bolus infusion) in 15 children with HIV infection. Furthermore, in eight of the children for whom data was available, in addition to high peripheral cortisol levels, neurologic dysfunction and hippocampal atrophy were noted on CT scan. These preliminary data suggest that in HIV-infected children an altered cortisol secretion may be associated with specific central nervous system damage.