Abstract:Labetalol, an agent with both alpha‐ and beta‐adrenoreceptor blocking properties, and the beta blocker propranolol were each given for one month to groups of 15 patients with essential hypertension. With either treatment, 11 of the 15 patients experienced decreased supine diastolic blood pressure to less than 90 mm Hg without evidence of fluid retention. Propranolol significantly increased plasma concentrations of uric acid and potassium, whereas labetalol significantly increased plasma concentrations of high‐density lipoproteins (HDL) and decreased the total cholesterol:HDL ratio; neither drug significantly changed renal function. During three additional months of labetalol treatment, there was a slight tendency to orthostatic decreases in systolic blood pressure as compared with the values after the initial month. Labetalol had variable effects on plasma renin activity and aldosterone excretion, but within individual patients the values were constant; there were close correlations between changes measured after one month and after four months for both renin (r= 0.86) and aldosterone (r= 0.94). The manifestations of labetalol's alpha‐blocking component appeared to be a small postural effect on systolic blood pressure and an increase in pla