The effects of intravenous iron, with and without androgens, was studied in a group of 39 patients treated by regular haemodialysis, almost all of whom had normal serum iron concentrations. Intravenous iron 1–2 g every 4 months produced a significant rise in haemoglobin from 6.3 to 7.9 g/dl in 17 female patients with their kidneys in situ (p < 0.001). In a group of 13 male subjects intravenous iron plus testosterone produced a similar rise in haemoglobin from 6.9 to 8.6 g/dl (p < 0.001). Nine nephrectomised patients showed no significant response to iron and androgens. There were no fatalities and no serious side effects in 500 courses of intravenous iron.