We studied blood pressure in relation to known drinking habits of 83,947 men and women of three races (83.5 per cent white). Using health-check-up questionnaire responses, we classified persons as nondrinkers or according to usual daily number of drinks: two or fewer per day, three to five per day, or six or more per day. As compared to nondrinkers blood pressures of men taking two or fewer drinks per day were similar. Women who took two or fewer drinks per day had slightly lower pressures. Men and women who took three or more drinks per day had higher systolic pressures (P less than 10(-24) in white men, and less than 10(-12) in white women), higher diastolic pressures (P less than 10(-24) in white men, and less than 10(-6) in white women), and substantially higher prevalence of pressures greater than or equal to 160/95 mm Hg. The associations of blood pressure and drinking were independent of age, sex, race, smoking, coffee use, former "heavy" drinking, educational attainment and adiposity. The findings strongly suggest that regular use of three or more drinks of alcohol per day is a risk factor for hypertension.