Criteria for the screening, diagnosis and therapy of primary aldosteronism (PA) were defined on the basis of its symptoms analysis in 40 PA patients. A diagnosis of PA was proved in 4.12% of 970 patients admitted for arterial hypertension. The presence of polyuria, nocturia, neuromuscular disorders, hypertension, hypopotassaemia, alkalosis, elevated urinary potassium excretion, improving after Spironolactone, was most valuable for the purposes of screening. High plasma aldosterone concentration (PAC) and suppressed renin activity (PRA) provided evidence of the presence of PA. The most successful technique to differentiate aldosterone producing adenoma (APA) from idiopathic hyperaldosteronism (IHA) proved to be adrenal phlebography combined with determination of PAC in the adrenal veins. APA was associated with a 5.9 fold higher PAC in the vein of the adenoma - affected adrenal in contrast with a symmetric PAC rise in both adrenal veins in IHA. A paradoxical decrease of PAC occurred in the peripheral blood of most patients with APA after standing up, but 23.8% exhibited the same orthostatic increase as IHA patients. In all APA patients, unilateral adrenalectomy eliminated the symptoms of hyperaldosteronism and improved or cured hypertension. Spironolactone was indicated preoperatively for all surgical candidates, for non-operated APA patients, and for all IHA patients.