Plasma aluminum (pAl) was measured in 58 patients coming from three centers using different preparation of dialysis water: deionizer (29 patients), softener (16 patients) and reverse osmosis (13 patients). Twenty five healthy subjects were used as controls. A deferoxamine test was performed to 11 of 19 patients with pAl between 40 and 200 micrograms/dl and a bone biopsy with double tetracycline staining was executed to 15 patients with pAl over 40 micrograms/dl. Mean pAl was 9.5 +/- 1.7 micrograms/dl in controls and 34.3 +/- 6.1 169 +/- 27.8 and 50.8 +/- 10.3 micrograms/dl in patients coming form centers using deionizers, softeners and reverse osmosis respectively. Seventy six percent of patients coming from centers using deionizers and 85% of patients coming from centers with reverse osmosis had pAl below 40 micrograms/dl and all had values below 200 micrograms/dl. Plasma aluminum had a increase of over 200 micrograms/dl in 6 of 11 patients in which the deferoxamine test was performed. Six patients had a positive staining for aluminum in bone biopsies (three with basal pAl over 200 micrograms/dl and one with a increase in pAL after deferoxamine < 200 micrograms/dl). Of these, 2 patients had a mixed osteodystrophy and 4 a low turnover bone disease. Centers with deionizers and reverse osmosis had very low aluminum levels in dialysis water and five of six patients with aluminum levels related bone disease came from the center using softener.