OBJECTIVE Restriction of alcohol intake is widely recommended in the treatment of hypertension. However, we have observed that alcohol may have biphasic effects on blood pressure in Japanese men with hypertension. METHODS Hypertensive men (n = 34) who habitually drank alcohol were randomly assigned to keep their drinking habits constant for 4 weeks, or to abstain (or reduce alcohol intake to a maximum of 15 mL/day) for 4 weeks in a crossover design. Amount of alcohol intake was recorded by each patient throughout the study. Office and 24-hour ambulatory blood pressure were measured at the end of both periods. RESULTS After alcohol restriction, mean (+/-SD) ethanol intake decreased from 66+/-26 mL/day to 11+/-10 mL/day. Office systolic blood pressure decreased slightly from 142+/-12 mm Hg to 139+/-11 mm Hg, and diastolic blood pressure decreased significantly from 95+/-7 mm Hg to 93+/-7 mm Hg in the low-alcohol period. Daytime systolic blood pressure fell by 3+/-9 mm Hg (P <0.05), but nighttime systolic blood pressure rose by 4+/-9 mm Hg (P <0.05) with restriction of alcohol intake. Thus, average 24-hour blood pressure did not change, although 24-hour heart rate and day-night difference in blood pressure decreased significantly in the low-alcohol period. CONCLUSIONS In Asian men with hypertension, restriction of alcohol intake reduces daytime blood pressure but not night-time or 24-hour blood pressure.