Vitamin D is one of the most important regulating agents in the development of bone mass. Therefore administration of calciferol along with calcium in patients with nutritional vitamin D deficiency leads to improvement of bone density. In patients with osteoporosis who do not respond to vitamin D, insensitivity of osseous tissue to the active metabolite of vitamin D - 1,25(OH)2 D3 - is involved or inadequate synthesis of active metabolites in the liver or kidneys. Administration of 1a-OH vitamin D3 and in particular 1,25(OH) 2D3 improves the general calcium balance in the organism and increases by direct osteoforming action the value of bone mass and improves its quality. Administration of active vitamin D metabolites is unequivocally better in treatment of involutional osteoporosis, either along with calcium or in combination with some antiresorption substance, in osteoporosis associated with chronic inflammatory diseases , after organ transplantation or glukcocorticoid treatment. Even patients with postmenopausal osteoporosis respond better to 1,25(OH)2D3 .

        Key words: Osteoporosis - Vitamin D - Calcitriol - Rocaltrol