The objective of this article is to test whether the concentration of potentially oxidizable lipids (polyunsaturated fatty acids [PUFA], total and free cholesterol) and lipophilic antioxidants (plasmalogens, vitamin E) in the fetal lung correlate with lung maturation (P/S ratio). In amniotic fluid palmitic/stearic acid (P/S) ratio, concentrations of PUFA, total and free cholesterol, vitamin E, and plasmalogens were measured. Ratio of PUFA to stearic acid (PUFA/S ratio) was determined in lung effluent of 15 preterm infants with IRDS and compared with values from 15 term healthy infants. Concentrations of plasmalogens, PUFA, total and free cholesterol increase significantly with increasing P/S ratio. No correlation of vitamin F with lung maturation has been found. The PUFA/S ratio is significantly lower in lung effluent of preterm (0.79 ± 0.27) when compared with term infants (2.02 ± 0.38). Our results suggest that the higher susceptibility of preterm infants for oxidative lung injury is not caused by an unfavorable ratio of oxidizable lipids to lipophilic antioxidants in surfactant, but rather by a lower amount of PUFA containing surfactant lipids. Our results are in accordance with data from Sosenko et al. who have shown that high levels of PUFA in the rat lung have a protective effect against oxygen-induced lung damage.