The administration of beta blockers has been useful in the treatment of essential hypertension. The anti-hypertensive effect of the beta-blocker sotalol was evaluated in 28 patients with essential hypertension. In all of the patients a determination of urinary aldosterone and plasma renin activity, before and after, three months of treatment with sotalol was done. In the pre-treatment tests, five patients (18%) had elevated renin values, in 13 (6%) renin was normal, and in 10 (36%) the renin activity in plasma was low. Treatment with sotalol caused normalization or significant lowering of diastolic pressure in the majority of cases with high or normal plasma renin. Patients with low plasma renin activity had less satisfactory results with the drug. Since there was no correlation between the lowering of arterial pressure and the degree of depletion of renin, we can conclude that anti-hypertensive mechanism of sotalol does not come from the decrease in secretion of renin. However our results suggest that patients with high renin respond better to treatment with sotalol, than cases with low renin levels.