Sodium balance and aldosterone secretion rate (ASR) were determined in patients with the hypertensive form of congenital adrenal hyperplasia. Three patients manifested a severe form of the disease. When on appropriate glucocorticoid therapy they were given a low Na intake, all 3 patients went into negative Na balance, while their ASR became abnormally low. Their inability to adequately enhance their ASR while production of desoxycorticosterone was suppressed by glucocorticoid treatment was probably responsible for the sodium loss. In a fourth patient with a milder form of the syndrome, during adequate therapy and a regular Na intake, the ASR was found to be at the lower limit of the normal range. On the 7th day of a 9 mEq Na diet, the ASR was lower than that observed in normal subjects.