Captopril is a specific inhibitor of kininase II which is responsible for the conversion of angiotensin I into the active angiotensin II and also for the inactivation of bradykinin. In different types of experimental and clinical hypertension, Captopril has a pronounced blood pressure-reducing action particularly when it is given together with a diuretic. Serious side-effects have hitherto restricted the use of Captopril to patients who do not respond or do not respond satisfactorily to routine antihypertensives. Since it has been shown that a considerable improvement in disturbed hemodynamics in hypertension and in certain forms of heart failure can be achieved with quite low doses of the preparation (2 x 2 mg daily) the use of Captopril may be indicated in greater amounts in moderate and severe hypertension.