Thirty patients suffering from WHO I-II class slight-moderate essential arterial hypertension were treated with a beta-blocker (Penbutolol) alone and once a day to assess its antihypertensive effectiveness and its affect on heart frequency, lipid metabolism and kidney function. The drug proved highly effective in reducing P.A.S. and P.A.D. values and no negative influence was documented on lipid metabolism, kidney function or heart frequency.