Six adult male Rhesus monkeys (T), treated with 0.5 mg/kg dexamethasone for 106 days, and 6 weight-watched controls (U), were studied postmortem with pathologic examination and cranial computerized tomography (CT). Cortical atrophy, as defined by perisulcal atrophy and ventricular dilatation, was found in 50% of each group, but marked changes were noted only among T. Adrenal, brain, and body weights were all lower among T (p less than 0.05). No significant histopathologic abnormalities were found. Our data suggest that CT changes of cortical atrophy may be caused by corticosteroid hormones alone, but are inconsistent and probably dependent upon individual susceptibility to the effects of corticosteroids.