Although the best known actions of vitamin D involve its regulation of bone mineral homeostasis, actions critical for a healthy skeleton, vitamin D exerts its influence on many physiologic processes. One of these processes is the immune system. Both the adaptive and innate immune systems are impacted by the active metabolite of vitamin D, 1,25(OH)₂D₃. In turn, the immune system is now recognized as having a major impact on the skeleton. In this review, I will examine the regulation by 1,25(OH)₂D₃ of immune function, then examine the evidence for such regulation as potential means of ameliorating the bone loss that accompanies the inflammatory state.