The proposed guidelines for antihypertensive drugs from the United States Food and Drug Administration (FDA) suggest that a trough: peak ratio (placebo corrected) of at least 50% should be a requisite for approval in the United States. It is apparent that many existing antihypertensive agents fail to meet this criterion. In contrast, the newer dihydropyridine calcium antagonist lacidipine has a trough:peak ratio greater than 60% which, combined with its other properties, indicates that it is suitable for once-daily administration in hypertension. There is evidence to suggest that a favorable trough: peak ratio may be beneficial in patients who are not fully compliant with the dosage regimen. In addition, a high ratio is indicative of small pharmacologically induced variability in blood pressure; indeed, lacidipine significantly reduces both systolic and mean blood pressure variability. Because blood pressure variability, independent of absolute pressure, is an important determinant of target-organ damage, there is reason to believe that agents that reduce variability may improve the morbidity associated with hypertension.