Blood pressure and heart rate exhibit a circadian rhythm, with both rising rapidly during the morning hours and then decreasing throughout the day to a nadir around 3 AM. Current evidence suggests a possible link between cardiovascular events, such as myocardial infarction and sudden cardiac death, which have been shown to occur most frequently during the morning hours, and the rapid rise in blood pressure and heart rate during this same time period. We review data from ambulatory blood pressure studies to ascertain which antihypertensive agents provide the most satisfactory control of blood pressure and heart rate during the hours of 6 AM to 12 noon. Of the forms of drug therapy studied, labetalol, a combined alpha- and beta-blocker, and two calcium channel blockers, nifedipine and verapamil, appear to be the most effective in blunting the rise in arterial blood pressure during these critical morning hours.