To investigate the efficacy and safety of losartan in the treatment of essential hypertension, 81 patients were randomly assigned to two groups. Patients in the first group(n =41) were given losartan 50 mg to 100 mg once a day; those in the second group( n = 40) were given benazepril 10 mg to 20 mg once a day. The treatment course lasted for a weeks. Ambulatory blood pressure, hepatic and renal functions, blood glucose were examined before and after therapy. Our results showed that the total efficacy rate in losartan group was 93％ while that in benazepril group was 90％. The efficacy was similar between the two groups. However, effect of 24 h blood pressure control by lossrtan was superior to than of benazepril. The adverse reaction of losartan was milder that that of benazepril. It is concluded that losartan is a safe, long-acting antihypertensive agent for mild and moderate hypertension with good patient tolerance and less adverse reactions.