Fifty nine patients suffering from slight or moderate essential arterial hypertension underwent hypotensive treatment. After one week of wash-out, therapeutic administration of tienilic acid in doses of 500 mg per day was begun; in the third week we combined a non diuretic hypotensive drug (prazosin, propranolol, alfametil-dopa). At the beginning of the study all patients underwent an ECG, a clinical cardiological examiniation, funduscopy examination, funduscopy examination, a heart X - ray in 3 standard positions and a routine blood test which was repeated during and at the end of the treatment. The patients' blood pressure taken in an upright and supine position, showed statistically significant reductions for both systolic and diastolic values in all 3 groups, whereas the routine blood tests gave evidence of a marked reduction in the uriacid, triglycerides and potassium levels. In order to correct the latter we had to administer high oral doses of potassium, and in one case admittance to hospital was necessary since the potassium level was lower then 2.5 mEq/l.