A clinical and laboratory examination was conducted with a hypotensive drug Katapresan used alone and in combinations with Reserpine and saluretics in 30 patients with stage II and III of essential hypertension. Katapresan was shown to be an active hypotensive agent, often effective in patients resistant to other drugs. For long-term therapeutic courses the most effective combination is Katapresan with Hypothiazide and Reserpine. Katapresan may result in a deceleration of atrioventricular conduction, a slowing down of the electric systole, a reduction of the contractile function of the myocardium. The drug does not affect the metabolism of potassium and sodium ions.