CAPD results in continuous peritoneal transfer of hormones and minerals involved in the pathogenesis of renal osteodystrophy (RO). Moreover, although CAPD patients seem to have better control of serum phosphate concentration than hemodialysis patients, the need for aluminum-containing phosphate binders (ACPB) may still be present. In a prospective study meant to investigate the evolution of RO, we obtained 79 bone biopsies in 29 uremic patients (20 male, 9 female; age 25-59, mean 46). Of these, 22 were obtained at the beginning of treatment, 24 after 24 months, 23 after 36 months and 10 after 60 months. All patients were treated with CAPD (Viaflex, Baxter 2-2.5 L x 4-5 bags/day; Ca(++) + 3.5, Mg(++) 1.5 mEq/L) as the first modality of therapy and received oral calcitriol, aluminum hydroxyde and/or calcium carbonate and magnesium hydroxyde in order to maintain serum calcium (Ca) and phosphorus within the normal range. Qualitative bone histology, bone Ca and magnesium (Mg) (Flame atomic absorption spectroscopy) and aluminum (Al) concentration (Graphite furnace atomic absorption spectrometry) were determined. CAPD achieves a good control of RO as indicated by the tendency toward a decreased incidence of mixed osteodystrophy and predominant hyperparathyroid bone disease and improvement of osteoid lesions. A defective Ca content of bone is persistent in the observed period and positively correlated to bone Mg concentration. An increased level of Al was shown in the serum and bone. The highest bone Al content was found among patients with predominant osteoid bone disease. Also in CAPD, patients consuming ACPB are at risk of bone Al accumulation despite the low Al levels in the dialysate.