Aging and associated increases in systolic blood pressure may cumulatively produce alterations in many blood pressure regulatory mechanisms that impair an older person's ability to adapt to hypotensive stress. Both age and hypertension impair baroreflex sensitivity and decrease compliance of the heart and vasculature. These changes increase the risk of hypotensive responses to activities that reduce cardiac preload and to conditions that produce tachycardia or eliminate atrial contraction. Common clinical examples include orthostatic and postprandial hypotension, nitrate intolerance, and atrial fibrillation. The increased intra- and interindividual variability in blood pressure, resulting from impaired homeostatic capacity, challenges established diagnostic criteria for hyper- and hypotensive syndromes and necessitates new multivariate approaches to research data analysis. Gerontologic investigations utilizing blood pressure measurements should examine individual as well as group responses, and stratify subjects by level of basal blood pressure to isolate the effect of aging from the effects of blood pressure elevation.