Thirty-seven osteodystrophic and chronically haemodialyzed patients have been treated for 1-22 months by means of 1,25(OH)2D3. Under treatment a marked improvement of symptomatology and radiographic findings has been observed in the majority of cases; from the haematochemical viewpoint a rise of calcemia and phosphoremia, a fall in alkaline phosphatase and a variable course of PTH have been observed. Several episodes of asymptomatic hypercalcemia ceased with posology reduction; only 3 cases needed stopping the treatment for this reason, one of them definitively; 12/37 cases needed hypophosphoric diets and increase in oral aluminium hydroxide doses to control hyperphosphoremia. The Authors conclude that, to achieve a correct management of a 1,25(OH)2D3 therapy for renal osteodystrophy, is mandatory a strict and accurate biochemical control: in this way is possible to obtain an effective modulation of the posology avoiding the appearance of side-effects as hypercalcemia and ectopic calcifications.