The optimal control of aluminium content in dialysis fluids has resulted in a decrease in the incidence of aluminium related bone disease (ARBD) and in the risk for aluminium toxicity. Nevertheless the problem has not disappeared. Bone biopsy with specific staining for Al remains the only reliable method for the diagnosis of ARBD. Currently there is not a total agreement on the reliability of serum Al levels and of the DFO test in the identification of patients with Al overload or toxicity. In a series of patients (mean age 48 +/- 14 years old) from our hemodialysis units we carried out bone biopsy and we studied the prevalence of bone aluminium overload and of ARBD and the usefulness of serum aluminium and of DFO test in their diagnosis. Seventy- three bone biopsies were evaluated by histomorphometric analysis and aluminium staining (Aluminon). Al overload was diagnosed when the Aluminon staining was positive independent of the bone surface covered with Al and of the bone formation rate (BFR). Patients were consider to have ARBD when aluminium covered > 25% of bone surface and BFR was < 0.031 micron 3/micron 2/day. Fifteen patients had aluminium overload while 7 patients were considered to have ARBD. Positive Aluminon staining appeared in all histopathological forms of renal osteodystrophy although it appeared mainly in patients with mixed lesion and osteomalacia. Most of the patients with adynamic bone disease had negative Aluminon staining. Patients with aluminium overload showed lower bone formation and mineralization rates. Serum aluminium levels below 40 micrograms/l were useful to exclude bone aluminium overload. Serum aluminium levels and DFO test were not specific in diagnosing aluminium overload or ARBD. A DFO test with an increment in serum aluminium over 100 micrograms/l in combination with a serum PTH below 200 pg/ml was useful to diagnose ARBD.