1alpha,25-dihydroxy-22-oxavitamin D(3) (maxacalcitol;OCT), a vitamin D analogue with reduced calcemic activity, showed potency 10 times greater than 1alpha,25 (OH) (2)D(3) in differentiation induction of HL-60 cells. In addition, OCT showed immunomodulating activity, anti-proliferative effect and a suppressive effect on PTH secretion in vitro. OCT suppressed the expression of PTH mRNA in both normal and nephrectomized rats, and up-regulated VDR in the parathyroid gland in uremic rats to the same degree as 1alpha,25 (OH) (2)D(3). The results of a comparison between OCT and 1alpha,25 (OH) (2)D(3) indicate that the dissociation between efficacy and side effects with OCT is greater than with 1alpha,25 (OH) (2)D(3) in uremic rats. In future, we expect that OCT would contribute a great deal to the dialysis field in clinical.