Phosphate binders that contain aluminum are usually prescribed to treat hyperphosphatemia in patients with chronic renal failure, but an accumulation of aluminum can lead to osteomalacia, encephalopathy and anemia. To evaluate the effect of CaCo3 on serum calcium and phosphorus as a alternative phosphate binder, we studied 13 patients on regular hemodialysis treatment. In basal period, some patients were administered Al(OH)3 and CaCO3, others only the former or the latter and others nothing. Al(OH)3 was stopped in all patients and CaCO3 was started or increased in all patients. A better control of sCa, sPi and sCa-Pi product was observed during only Ca supplementation, despite Al(OH)3 discontinuation. Some patients developed a mild hypercalcemia and hypophosphatemia, especially in those who had a normal predialytic sPi. Therfore considering the dialysate Ca concentration according to individual need and the adjustment of amount of CaC3 to avoid these risks can be recommanded with the dual objective of keeping a positive Ca balance and correcting hyperphosphatemia.