AbstractTwenty patients, known to have essential hypertension, were treated for an average period of 30 months with alprenolol (Aptin®). Initially, the dose reponse to 200 mg up to 800 mg daily was observed. Nine patients were well controlled on alprenolol alone (mean 555 mg daily). The mean decrease at 36 months was 31/21 supine and 28/25 standing in comparison with the initial placebo readings. Ten other patients, who were only partially controlled on alprenolol alone, were eventually well controlled by a combination of alprenolol with either hydralazine or chlorthalidone.No difference was observed in the antihypertensive effects of propranolol and alprenolol in a comparative exercise study on six of the patients.One patient was withdrawn from the study. Side‐effects of transient lassitude occurred in four patients. No signs of bronchial obstruction, postural hypotension or cardiac decompensation were observ