ABSTRACTOver 100000 renal failure patients are treated by dialysis in the European Community (EC), and the number is rapidly increasing due to better medical care. The full importance of the quality of water used for renal dialysis is only now being recognized. Aluminium intoxication, first described in the early 1970s, highlighted the need for adequate treatment of water used to prepare dialysate. Other materials harmful to dialysis patients, such as chloramines, may arise as a result of water treatment practice. The paper presents a European‐wide assessment of the problems of trace contaminants in dialysis feed water, and examines some contaminant sources in mains water in the light of dialysis water standards and the current treatment techniques available.