A total of 1,026 patients undergoing haemodialysis as the only chronic treatment were studied in all the dialysis units of the Veneto region, Italy. Aluminium was determined in water, dialysis fluids, and patients’ serum. Aluminium mean concentration was 9.1 µg/l in tap water and 13.3 and 15.7 µg/l in bicarbonate and acetate haemodialysis fluids, respectively. Patients’ serum aluminium mean level was 52.0 µg/l with the following frequency distribution: 59.2% below 60 µg/l, 25.5% between 60 and 100 µg/l, and 15.3% above 100 µg/l. The mean serum aluminium level was higher in patients undergoing haemodialysis with aluminium concentration in fluids over 10 µg/l. This was true also in patients not receiving aluminium hydroxide. Furthermore, we found higher average serum aluminium in those treated with aluminium hydroxide more than 3 g/day. No relationship was found between serum aluminium and sex, age, dialytic age, parathyroid hormone, and vitamin D treatment. Moreover, the patients with serum aluminium above 100 µg/l had higher serum alkaline phosphatase and lower mean cell volume values. Thus, in our haemodialysis population aluminium overloading occurred in spite of low concentration in water and fluid, and it was a result more of fluid pollution (over 10 µg/l) than aluminium hydroxide ingestion (o