Primary hyperaldosteronism is the most common secondary form of hypertension. Diagnosis of this entity is recommended in hypokalemic hypertension, in therapy-resistant hypertension (at least three 3 drugs and RR > 140/90 mmHg), and in adrenal incidentalomas (= incidentally discovered adrenal tumors). For screening, the ratio between plasma aldosterone (PAC) and plasma renin concentration (PRC) should be measured. In the assessment of PAC/PRC ratio, the discontinuation of some antihypertensive medication and assay-specific cutoff values must be noticed. After a positive screening test, saline infusion test should be done as confirmatory test. In contraindications/impracticability of this test, 24-h urine collection for aldosterone-18-glucuronide under high-sodium diet can be used as alternative confirmatory test. After confirmation of primary hyperaldosteronism, differential diagnosis between aldosterone-producing adenoma and idiopathic hyperaldosteronism has to be done. For this approach, adrenal CT or MRT, posture test and adrenal vein catheterization as gold standard test are available. Whereas therapy of aldosterone-producing adenoma is surgery, idiopathic hyperaldosteronism is to be treated medically by spironolactone.