METHODS A 39-year-old patient presented with normokalaemic therapy refractory arterial hypertension despite of four antihypertensive drugs for further diagnostics. METHODS Ultrasound displayed no evidence of renal artery stenosis. Furthermore, the kidneys were normal sized and morphologically without pathological findings. Renal function was normal. Free cortisol and catecholamine levels in a 24-hr-urine sample were within the normal range. Plasma renin activity was reduced and both the plasma aldosterone concentration and the aldosterone to renin ratio were elevated. A saline infusion test showed no suppression of the plasma aldosterone concentration, nor did an orthostatic testing show an increase. MRI revealed an adenoma of the right adrenal gland. METHODS The results were consistent with primary aldosteronism due to an aldosterone-producing adenoma of the adrenal gland. The patient underwent laparoscopic adrenalectomy. The histological findings confirmed an adenoma of the adrenal gland. Three months later, blood pressure was normal under a single treatment regimen with an AT(1) receptor blocker. CONCLUSIONS Screening for endocrine causes of hypertension is recommended in young patients, therapy refractory hypertension, and in hypokalaemic hypertension. Normokalaemia does not exclude primary aldosteronism as the underlying cause of hypertension.