Arotinolol, a new alpha and beta receptor antagonist, was administered in 27 essential hypertensive patients for 8 weeks in order to evaluate the antihypertensive effect and side effects. The dose were 10mg to 15mg given twice a day. The results are as follows : 1) Before medication, systolic and diastolic blood pressure in sitting, supine and erect position were 173.1+/-3.2/105.8+/-1.8, 171.1+/-3.6/86.7+/-2.0 and 169.3+/-2.6/97.2+/-2.1mmHg. 2) After 8 weeks treatment moderated to marked antihypertensive effect was observed in 74.0%(in systolic blood pressure) and 81.4%(in diastolic blood pressure) respectively in sitting position. 3) There was a significant reduction of pulse rate from 73.0+/-2.5 beats per minute on the beginning of the treatment to 63.4+/-5.2 beats per minute after 8 weeks of medication. 4) There was no significant change in hematocrit, WBC, serum lipid, GOT, GPT, BUN and creatinine. But fasting blood sugar was reduced from 95.3mg% to 81.5mg% with treatment. 5) The side effects of arotinolol were gastrointestinal symptoms(15%), fatigue(11%), dizziness(7%) and insomnia(3%). But these side effects were not severe enough to discontinue medication. In summary, arotinolol seemed to be an effective antihypertensive drug in treating mild to moderate hypertension without significant side effects.