Studies performed during the last years indicate the importance of vitamin D not only in calcium and phosphorus homeostasis but also in the pathogenesis of inflammatory and proliferative diseases. Vitamin D deficiency might be caused not only by pathological processes but also by therapeutic procedures. In this review indications for systemic cholecalciferol supplementation and topical application of vitamin D metabolites and synthetic analogues are presented. Calcitriol, tacalcitol and calcipotriol are used in topical treatment of plaque psoriasis. Several lines of evidence emphasize the usefulness of vitamin D derivatives in many unregistered indications.