The aim of this study was to determine the validity of our previous hypothesis of adrenal 11 beta-hydroxylase (11-OH) dysregulation in "essential" low-renin hypertension.A comparison was made between 30 hypertensive patients and 30 age-matched controls (NC) in basal conditions and after ACTH stimulation (ACTH 1-17) test. The 11-deoxycortisol (S) and deoxycorticosterone (DOC) integrated areas under the curve (AUCs) of stimulus were significantly higher in the hypertensives (p < 0.001) and pointed to adrenal 11-OH dysregulation.The ACTH 1-17 test detects impairment of 11-OH activity of probable genetic origin. The relative mineralocorticoid excess thus provoked could be an additional cause of "essential" low-renin hypertension.