Hypovitaminosis D (LoD, serum 25 hydroxyvitamin D levels below 32 ng/ml) has become a major concern for an aging population by virtue of its association not only with bone loss and fractures but also with virtually all major diseases and syndromes affecting aging persons. The key target population for studying LoD and vitamin D supplementation is the rapidly growing sedentary segment of community-dwelling independent elderly persons who have the greatest prevalence of LoD and increased vulnerability for physical disability and frailty. Such persons can be highly resistant to lifestyle changes that would increase their physical activity. Several recent studies suggest that vitamin D supplementation would enhance physical performance in sedentary older persons and thereby delay or prevent their decline and disability. Our published and preliminary studies document LoD as a major problem in south Florida, particularly in the older male veteran population, and demonstrate the feasibility of robust supplementation with vitamin D using large, but safe, doses of vitamin D. In concert with our expertise in assessing physical performance in older persons, these studies open the way to a randomized clinical trial to ascertain whether robust vitamin D supplementation in sedentary older male veterans with LoD will improve the ability to perform physical tasks needed for maintaining independence. Sedentary male veterans, ages 65 to 90, will be enrolled in our VIVA-VA Study (VitaminD In Vulnerable Adults in the VA), a double-blind, placebo-controlled, randomized clinical trial aimed at ascertaining whether robust supplementation with vitamin D improves physical performance as tested by the Short Physical Performance Battery (SPPB).