The purpose of these studies was to assess the effect of 6 month calcidol treatment on Ca and PO4 metabolism in haemodialyzed patients. During 3 and 6 month on alpha calcidol therapy, there was significant increase of total and ionized Ca (p < 0.05; p < 0.01 respectively). After 6 months on alpha calcidol therapy there was significant decrease of alkaline phosphatase level (p < 0.05) and increase in bone density (up to 82%, p < 0.05). The study has shown that appropriate use of alpha calcidol could be effective in treatment of Ca and PO4 disbalance in haemodialyzed patients.