There is increasing evidence that D-hormones (active vitamin D metabolites) are effective agents in preventing posttransplantation bone loss of various organs. This effect may relate to several mechanisms including reversal of secondary hyperparathyroidism from cyclosporine, reversal of corticosteroid effects on bone, or immunomodulatory effects with corticosteroid sparing. Further clinical trials are necessary to establish their comparative efficacy to other agents, but D-hormones should be considered as prophylactic therapy in patients undergoing organ transplantation.