Aging is associated with increased fracture risk. Among the many contributing factors, reduced bone mineral density is highly correlated with this risk. Nutritional factors, i.e. protein, calcium, and vitamin D intake, are essential for maintenance of the skeleton throughout the lifespan and are often compromised in the elderly. Vitamin D is also derived from conversion of precursors in the skin that is stimulated by sunlight. Decreased mobility and avoidance of the sun contribute to vitamin D deficiency in the elderly. The skeletal effects of vitamin D are two-fold: it ensures mineralization of the organic matrix of bone and it mediates mobilization of stored calcium and phosphate from bone to blood to achieve mineral homeostasis. Inadequate levels of vitamin D produce a secondary increase in release of parathyroid hormone that stimulates bone resorption and can result in osteoporosis. If coupled with insufficient intake of calcium, vitamin D deficiency results in osteomalacia. With aging, there is reduced absorption of the vitamin from the diet, reduced conversion to its active metabolites, and resistance to its action in the intestine and in bone. Correction of vitamin D deficiency is an inexpensive task and may require education of clinicians as well as the public. In sum, vitamin D deficiency is prevalent in the elderly and, to correct the adverse skeletal effects, it should be diagnosed, treated, and prevented.