The aim of the study was to evaluate dexamethazone test in a patient with primary aldosteronism caused by an adrenocortical adenoma. We observed a 50% decrease of plasma aldosterone as in glucocorticoid suppressible aldosteronism (GSA) but absolute value of aldosterone remained higher than 40 pg/ml. Basal plasma and urinary values of 18 OXO and 18 OH cortisol were not significantly elevated as in GSA. Inversely, the evaluation of 11 beta-hydroxylase activity of mineralocorticoids was in favor of a benign adrenal tumor.