Background The association between alcohol and blood pressure (BP) may be related to the temporal sequencing of alcohol use and BP measurement. We investigated the effects of single and repeated intakes of alcohol on 24-hour BP.Methods and Results Fourteen male habitual drinkers with essential hypertension were placed sequentially on a 4-day control phase: a nonalcoholic drink with the same calories as alcohol was given at dinner (5 pm to 6 pm) and a 7-day drinking phase: alcohol (ethanol, 1 mL/kg) was given at dinner under standardized conditions. Ambulatory BP measurements were performed on day 3 of the control phase and on days 1 and 7 of the alcohol phase. The average 24-hour systolic and diastolic BPs on day 1 were significantly lower than those in the control phase and on day 7. Between 6 pm and midnight, both systolic and diastolic BPs on days 1 and 7 (121+-2/73+-1 and 126+-4/75+-2 mm Hg, respectively) were significantly lower than those in the control phase (139+-4/83+-2 mm Hg). Between midnight and 8 am (6 to 14 hours after the last drink), both systolic and diastolic BPs on day 7 (138+-4/83+-2 mm Hg) were significantly higher than those in the control phase (131+-4/79+-2 mm Hg) and day 1 (129+-3/77+-1 mm Hg). Between 8 am and 3 pm, BPs showed no difference among the three phases.Conclusions A single intake of alcohol has a depressor effect on BP that lasts for several hours after drinking, while repeated intakes for 7 days have both depressor and pressor effects according to the differences in time intervals after the last drink. This study suggests that the chronic effects of alcohol on BP might be overestimated when based on casual BP measurements alone. (Circulation. 1994;89:2626-2633.)