Maintaining functioning among older men and women is an important public health goal as the U.S. population lives longer with chronic disease. Lower extremity peripheral arterial disease (PAD) affects 12% of men and women age 65 and older. This project will study the independent impact of PAD on lower extremity functioning and social independence among men and women age 55 and over. We will determine whether the ankle brachial index (ABI), an accurate, reliable measure of lower extremity arterial perfusion, predicts baseline and subsequent lower extremity function. Our primary specific aims are 1)To assemble a cohort of 470 men and women with PAD and 150 men and women without PAD, all age 55 or older, and follow them prospectively for up to 38 months; 2)To define the relationship between baseline lower extremity functioning and baseline lower extremity arterial perfusion as measured by the ABI; 3)To determine the relationship between the rate of decline in lower extremity functioning over 24 months follow up and baseline lower extremity arterial perfusion as measured by the ABI; 4)To determine whether current cigarette smoking, lack or regular exercise, diabetes mellitus, and lower physical activity levels are associated with greater functional decline among PAD subjects, independent of the ABI level. We will test the hypotheses that 1)Lower extremity arterial perfusion correlates directly and independently with lower extremity function; 2)Lower extremity function among PAD subjects deteriorates at a predictable rate over time; 3)PAD subjects with a lower ABI level experience greater declines in lower extremity function over time; 4)PAD subjects who smoke, are diabetic, do not regularly exercise, or have lower physical activity levels experience greater decrements in lower extremity function over time, independently of their ABI level. In an ancillary study, we will obtain blood samples and determine whether specific hemostatic factors and genetic polymorphisms are associated with higher rates of cardiovascular events and progression of PAD. Results of this study will be used to develop subsequent intervention studies designed to improve quality of life and prevent functional decline among men and women with PAD.