To study the time course of alcohol effects on blood pressure (BP), we examined morning and late evening home BP for 4 weeks in a regular alcohol consumption period and for 4 weeks in a alcohol restriction period in 30 Japanese men with essential hypertension (52 +/- 2 years, m +/- SE) in a randomized crossover study. Mean daily intake of alcohol were 66.5 +/- 4.7 and 10.2 +/- 1.9 ml, respectively. At the end of the regular alcohol period, morning BP had increased by 4.4 +/- 1.1/2.9 +/- 0.8 mmHg but evening BP had decreased by 7.4 +/- 1.9/5.7 +/- 1.7 mmHg. The depressor effect of alcohol on the evening BP was evident from day 1 to week 4, while the pressor effect on the morning BP was significant from week 2 regardless of the order of the two periods. These results confirm the biphasic effect of alcohol on BP, and suggest that the status of alcohol intake may markedly influence the morning-evening BP difference.