Ninety-one community-dwelling postmenopausal women with baseline 25(OH)D of 10-30 ng/mL received oral vitamin D₃, 2300 or 2500 IU, daily for 4-6 months. Serum 25(OH)D, cholecalciferol (D₃), and 24,25(OH)₂D were measured before and at the end of supplementation to determine if metabolite concentrations allow prediction of the 25(OH)D level attained.