The prevalence of primary hyperaldosteronism is 5-10% of all hypertensive patients, and clearly above the estimated prevalence in the past. In nearly 30% of patients with therapy resistant hypertension, primary hyperaldosteronism is detected if they are investigated thoroughly. This will result in 1.5 to 2.5 million people in Germany suffering from primary hyperaldosteronism. Besides efficient diagnostic procedures, an effective treatment is of increasing importance. The aldosterone-producing adenoma (Conn's syndrome) is primarily cured by operation, in most cases performed endoscopically. Bilateral hyperplasia, which is found in two-thirds of primary hyperaldosteronism, is treated primarily by mineralocorticoid receptor antagonist: 12.5-50 mg/day spironolactone (in case of anti-androgenic side-effects alternatively by 50-100 mg/day eplerenone). If the blood pressure can not be lowered by this first-line treatment, an additional treatment with potassium-sparing diuretics, calcium-antagonists, ACE-inhibitors or angiotensin-2-antagonists is necessary. The start of medication should be closely monitored by serum electrolyte and creatinine controls.