Iron overload, which is a common complication in haemodialysis patients, is known to enhance bacterial growth and virulence, and to alter phagocytosis. We reviewed the data of 61 haemodialysed patients to clarify the clinical relevance of iron status to the risk of bacterial infection. Increased concentrations of serum ferritin were associated with a greater infection rate (P less than 0.0025), which was already true for ferritin values between 500 and 1000 micrograms/l (P less than 0.025). Furthermore, in 21 iron-overloaded patients treated with an iron-chelator (desferrioxamine), the infection rate decreased from 1/19 patient-months to 1/112 (P less than 0.005), and returned to previous values when desferrioxamine was stopped. Our results demonstrate the importance of haemosiderosis in the increased susceptibility of haemodialysed patients to infections; this susceptibility is decreased by desferrioxamine therapy, which probably acts by restoring phagocytosis and reducing the bioavailability of iron for pathogens.