To evaluate the hypotensive effect of dilevalol which has a nonselective blocking action on beta receptors with selective beta2 agonist actcvity, We performed a prospective clinical study for 8 weeks in 31 patients with essential hypertension(mean age : 52+/-9, mean sitting blood pressure : 158/101mmHg) without concomitant heart failure, coronary heart disease, conduction disturbance or renal impairment. The daily dose of dilevalol was 200-400mg. The results were as follows ; 1) After 8 weeks of treatment with dilevalol, average sitting systolic and diastolic blood pressures reduced to 138+/-8mmHg(13%), 84+/-5mmHg(17%) respectively(p<0.01, 0.01). 2) After 8 weeks of treatment with dilevalol, 28(90%) out of the 31 hypertensives showed good hypotensive effect ie, : sitting diastolic blood pressure decreased to below 90mmHg. 3) Pulse rate decreased slightly from pretreatment average of 75+/-8 beats per minute to 70+/-6 beat per minute at the end of 6 weeks of treatment but went back to pretreatment value lastly. 4) Average body weight, serum levels of total cholesterol, HDL cholesterol, triglyceride, AST, ALT, BUN, creatinine, sodium and potassium were not significantly changed from the pretreatment values. 5) A few side effects in order of frequency were epigastralgia, fatigue, cold extremities and dizziness. These results suggest that dilevalil may be used as an effective first line monotherapeutic antihypertensive agent in mild to moderate hypertensives without significant limitations.