16 patients with recurrent staphylococcal furunculosis but without anaemia had significantly lower serum iron concentrations than normal laboratory reference values, 8 controls with single furuncles, or 10 controls with acne conglobata. There were no significant differences in serum glucose or iron binding capacity between the groups studied. Furunculosis resolved after 3-4 weeks' treatment with iron supplements in all but 1 patient. The relation between iron and susceptibility to infection is unclear, but merits further investigation.