The bleomycin assay measures non-transferrin-bound iron, able to catalyze free radical reactions, in human plasma. No bleomycin-detectable iron is present in plasma from healthy adults. However, plasma from 3/15 premature babies was positive in this assay. Plasma from 52 apparently-healthy term babies was analyzed and 11 were positive in the bleomycin assay. Hence not only some premature but also some full-term apparently-healthy babies may be at risk of severe oxidative damage.