 Active vitamin D analogs have been the mainstay of treatment for patients on hemodialysis with mineral and bone disease MBD for the past decade. Intravenous calcitriol is an active vitamin D analog which is nearly identical to natural 1, 25 Vitamin D3. Calcitriol results from the hydroxylation of previtamin D3 in the liver and kidney. Paricalcitol, 19-nor-1 , 25-dihydroxyvitamin D2, is a newer agent vitamin D analog. This agent is believed to have an effect more specific to the parathyroid gland, and less specific to absorption of calcium and phosphorus from the gut. Although both formulations appear equally effective in suppressing parathyroid hormone PTH, studies have suggested a greater calcemic effect with intravenous calcitriol as compared to paricalcitol 1. Due to this, paricalcitol is the predominant active vitamin D analog used in hemodialysis patients in the United States. Two recent changes in the management of hemodialysis patients will likely reduce the amount of active vitamin D analogs used in the near future: the liberalization of PTH goals according to international guidelines, 2 and the implementation of bundled payments for dialysis by Medicare. These changes challenge previous studies that have analyzed the safety and efficacy of these medications. The purpose of this prospective, randomized, cross-over study will be to determine whether calcitriol is as safe and effective as paricalcitol in the treatment of MBD in hemodialysis patients using the revised KDIGO parathyroid hormone targets. Our hypothesis is that calcitriol will be as equally safe and effective as paricalcitol in the treatment of MBD in hemodialysis patients. 