The arterial blood pressure (BP), the ratio between gram myocardial mass per 100 g body mass (R), the plasma renin activity (PRA) and the aldosteron content in the blood plasma (PA) were investigated in a model of renal hypertension, 30 days after the operation, in the following groups of male Wistar rats: operated and treated throughout the entire experimental period with captopril Pharmachim in a dose of 30 mg/kg body mass twice daily orally, and two control groups--operated and treated with saline, and non-operated animals of the same age, treated only with saline. BP, R and PA increase significantly in the control group with experimental hypertension. In the group treated with captopril PRA was more than doubled compared with the two control groups, with a considerable decrease in PA compared with the control group with hypertension. The results obtained for the captopril-treated experimental group (with the exception of PRA) are identical and close to the data for the control non-operated animals, i.e. the treatment of the experimental animals with captopril prevents the development of arterial hypertension and of myocardial hypertrophy with the coarctation hypertension model used.