Lanthanum carbonate is a highly effective phosphate binder with significant potential as a treatment for hyperphosphatemia in patients with end-stage renal disease (ESRD). Here, the results of a placebo-controlled, dose-ranging study are presented. 196 patients (> or = 18 years) receiving hemodialysis for at least 6 months entered a 1- to 3-week, single-blind, placebo run-in phase. Of these, 145 patients were randomized to a double-blind phase in which they received placebo or lanthanum carbonate in daily lanthanum doses of 225, 675, 1,350 or 2,250 mg for 6 weeks. Serum levels of phosphorus, calcium and parathyroid hormone, and adverse events were monitored throughout the study. The intent-to-treat analysis (n = 144) showed significant dose-related reductions in serum phosphorus at lanthanum doses of 675, 1,350 and 2,250 mg. After 6 weeks of treatment, phosphorus levels were significantly lower in the lanthanum groups receiving 1,350 mg/day and 2,250 mg/day, compared with the placebo group (respective changes from randomization: -0.95 +/- 1.39 mg/dl (-0.31 +/- 0.45 mmol/l), -1.13 +/- 2.01 mg/dl (-0.36 +/- 0.65 mmol/l), 0.75 +/- 1.47 mg/dl (0.24 +/- 0.47 mmol/l), p < 0.001). Significant reductions in serum phosphorus, compared with placebo, occurred in the lanthanum 1,350 mg/day group from the second week of treatment and in the 2,250 mg/day group from the first week of treatment. Adverse events were mainly gastrointestinal (e.g. nausea and vomiting). Treatment-related adverse events occurred in 39% of patients treated with lanthanum carbonate and 44% of the placebo group. Lanthanum carbonate is an effective and well-tolerated agent for the short-term treatment of hyperphosphatemia in patients with ESRD.