Acebutolol was given to a group of 23 subjects with essential arterial hypertension associated with tachycardia at rest. In 70 p.cent of the cases, arterial blood pressure was rapidly influenced by the treatment. The favorable results are mostly-but not exclusively-found among the subjects with the highest initial sympathetic reactivity and renin plasmatic activity. However, there is no correlation between the quality of the result and the degree of reduction of renin activity or heart rate.