In the past decade, there has been accumulating evidence indicating that vitamin D may provide great health benefits. Indeed, it has been shown that vitamin D deficiency not only causes bone and mineral disturbances but also may increase the risk of many common chronic diseases. Since very few foods contain vitamin D, humans depend on sun exposure to satisfy their requirements for vitamin D. However, factors related to the location, climate, aging, skin pigmentation, and use of barriers to protect from the sun light contribute to limit the synthesis of vitamin D in the skin. Vitamin D deficiency is highly prevalent in the general population and even more common in patients with chronic kidney disease (CKD). Certain conditions associated with CKD such as protein losses and the decreased food intake can predispose these patients to hypovitaminosis D. The interest in the nutritional status of vitamin D of CKD patients has been renewed after the recognition that low circulating levels of 25 hydroxyvitamin D, and not only of the vitamin D active form (1,25 dihydroxyvitamin D), can contribute to the development of secondary hyperparathyroidism. Therefore, vitamin D supplementation with either ergocalciferol or cholicalciferol has been recommended to restore and maintain adequate vitamin D status in CKD.