This chapter provides a summary of the literature including results from large trials, meta-analyses, and recent major recommendations. Two well-accepted and recent recommendations include those from the Agency for Health Research and Quality on calcium and vitamin D supplementation and from the Institute of Medicine's dietary reference intakes for calcium and vitamin D. This review suggests that there is strong evidence for synergistic roles of calcium and vitamin D in maintaining bone health in postmenopausal women, but the correlation between vitamin D alone and bone health is overall inconclusive.