In 25 hypertensives (42 +/- years), predominantly at stage I according to WHO-criteria, by the application of daily 5 +/- 4 mg prazosine and as combination of 9 +/- 6 mg with 73 +/- 31 mg propranolol the blood pressure normalized itself from on an average 183 to 148 mgHg systolically and 113 to 93 mgHg diastolically. In a long-term experiment confirmable also echocardiographically prazosine alone decreased the afterload of the heart in an unchanged high energy requirement at rest, and in a submaximal ergostasis the aerobic metabolic situation deteriorated. This could again be balanced by the combination with propranolol, whereby oxygen pulse, product of the pressure frequency and PWC 130 even improved. Function and size of the left ventricle remained echocardiographically uninfluenced in the two forms of therapy.