The antihypertensive effects of once-daily 15mg dose of tripamide(Normonal(R)) were observed in 30 cases of essential hypertension, and the results were as follows; 1) Mean drop in systolic and diastolic pressure were 30 mmHg and 16 mmHg, respectively. 2) In 76.7% of cases, good or fair control of blood pressure was resulted. 3) There was no significant difference in heart rate before and after treatment. 4) There was no significant difference in serum K, BUN, and FBS before and after treatment. 5) There was no any other side effect which required discontinuing the treatment.