The ACTH-cortisol axis was studied in 15 hemodialysis patients. Basal plasma cortisol concentrations were found to be elevated and ACTH to be in the high normal range. Cortisol responded normally to exogenous ACTH, but neither cortisol nor ACTH were suppressed in response to oral dexamethasone. 11-Deoxycortisol and ACTH concentrations did not rise normally in response to either oral or iv metyrapone. We conclude that standard testing of the ACTH-cortisol axis in dialysis patients yields results suggesting Cushing's syndrome.