Oxidant lung injury is widely regarded as a risk factor for bronchopulmonary dysplasia, but in vivo evidence of this association is limited. F2I have been shown to be a highly sensitive and specific marker of lipid peroxidation in vivo. In order to determine if F2I from lung predicted BPD, F2I levels were measured in TBA obtained from 28 ventilator-dependent premature infants between 12 and 24 hours after birth. TBA levels of the inflammatory mediators LTB4 and IL-8 were also measured. The infants had a mean birth weight (±SD) of 883 ± 195 g, gestational age (GA) 27.5 ± 2.0 wk, and were receiving an FIO2 = 0.56 ± 0.19. When assessed at 36 weeks post-conceptional age, 14 infants had an adverse outcome (either BPD or death) and 14 infants were alive without BPD. Univariate analysis revealed that F2I, LTB4 (but not IL-8), GA, and FIO2 were significantly associated with this adverse outcome. Further analysis indicated that the association of F2I and LTB4 with the adverse outcome at 36 wk post-conceptional age was independent of GA and FIO2, and that F2I and LTB4 were significantly correlated with each other. Analyses limited to infants alive at 36 wk post-conceptional age gave similar results. These results indicate that lung lipid peroxidation occurring within the first 24 h after birth is associated with either death or BPD when assessed at 36 wk post-conceptional age, and that this association is independent of GA and intensity of oxygen exposure, and may involve an inflammatory process.