Vitamin D has played a central role in the nephrologist's armamentarium, with active vitamin D analogues enjoying broad use for treatment of secondary hyperparathyroidism. Increasing data are now coming to light about the broader biological actions of vitamin D, including wide-ranging effects in several endocrine pathways, cardiovascular disease, infectious disease, and even the progression of chronic kidney disease (CKD). As additional agents are emerging to help with control of metabolic bone disease, these nontraditional pathways of vitamin D action will become increasingly important to consider when formulating a treatment plan. Although the only approved use for vitamin D analogues in CKD is the treatment of secondary hyperparathyroidism, well-conducted clinical trials may soon broaden the scope of this therapy. This article reviews the role of vitamin D therapy in CKD and looks to the answers that future research may bring.