Lanthanum carbonate (Fosrenol(TM), Shire Pharmaceuticals) is a novel treatment for hyperphosphataemia. In this open-label study, we compared the effects of lanthanum carbonate and calcium carbonate on bone in dialysis patients. Paired bone biopsies were taken, at baseline and after 1 year of treatment, in 33 lanthanum- and 30 calcium-treated patients. Serum phosphate levels were well controlled in both groups and lanthanum carbonate was well tolerated. After 1 year of lanthanum carbonate treatment, five of seven patients with low bone turnover at baseline and four of five with hyperparathyroidism developed a more normal bone turnover. Only one; lanthanum patient developed adynamic bone compared with six in the calcium group. Analyses of data so far indicate that lanthanum carbonate does not have any adverse effects on bone.