Therefore, the present study compared the efficacy of two maintenance therapy protocols, i.e., oral administration of alfacalcidol (an oral vitamin D preparation) at a dose of 1.0 ug/day (higher-dose group) or at a dose of 0.25 ug/day (lower-dose group), in patients with secondary hyperparathyroidism who responded to initial maxacalcitol therapy, resulting in the control of iPTH to < 150 pg/mL.