After successful renal transplantation there is continuing malabsorption of calcium and phosphorus. This is due in part to impaired glomerular filtration rate, and in part to the action of steroid on calcium and phosphorus absorption. The effect of steroids is most marked over the first 18 months after transplantation and causes significant malabsorption of calcium and phosphorus even though good graft function is established. Calcium and phosphorus malabsorption can be improved by exogenous 1,25-dihydroxy vitamin D (oral 1α-OH D3 or 1,25-[OH]2D3)