Chronic exposure to elevated glucocorticoid (GC) levels in Cushing's syndrome (CS) is associated with deficits in cognitive function. It has already been shown that CS patients scored significantly lower than controls on several aspects of cognitive function (J. Int. Neuropsychol. Soc. 6 (2000) 20). In the present study, 13 subjects who presented with CS were investigated one year after surgical treatment to determine the extent to which the effects of hypercortisolism on cognitive function are reversible. Subjects were evaluated with a battery of tasks, similar to the original battery of a year earlier and including tests of attention, visuospatial processing, memory, reasoning and verbal fluency. Except for one task of visual organization, the results showed little change in performance, suggesting that prolonged exposure to high levels of GC can cause long-lasting deleterious effects on cognitive function. The data suggest that correction of hypercortisolism is not necessarily correlated with short-term improvement in cognitive function.