Arterial stiffness has been proposed as an indicator of vascular aging. We aimed to examine this concept by analyzing associations of arterial stiffness with age, subjective and objective measures of physical functioning, and self-reported functional limitation. We measured aortic pulse wave velocity by applanation tonometry among 5392 men and women aged 55 to 78 years. Arterial stiffness was strongly associated with age (mean difference [SE] per decade: men, 1.37 m/s [0.06 m/s]; women: 1.39 m/s [0.10 m/s]). This association was robust to individual and combined adjustment for pulse pressure, mean arterial pressure, antihypertensive treatment, and chronic disease. Participants took an 8.00-ft (2.44-m) walking speed test, a spirometry lung function test, and completed health functioning and (instrumental) activities of daily living questionnaires. Associations of stiffness and blood pressure with physical function scores scaled to SD of 10 were compared. One-SD higher stiffness was associated with lower walking speed (coefficient [95% CI]: -0.96 [-1.29 to -0.64] m/s) and physical component summary score (-0.91 [-1.21 to -0.60]) and poorer lung function (-1.23 [-1.53 to -0.92] L) adjusted for age, sex, and ethnic group. Pulse pressure and mean arterial pressure were linked inversely only with lung function. Associations of stiffness with functional limitation were robust to multiple adjustment, including pulse pressure and chronic disease. In conclusion, the concept of vascular aging is reinforced by the observation that arterial stiffness is a robust correlate of physical functioning and functional limitation in early old age. The nature of the link between arterial stiffness and quality of life in older people merits attention. (Hypertension. 2011;57:1003-1009.). Online Data Supplement