Chronic lung disease of prematurity (CLD) remains a common cause of morbidity and mortality in preterm infants. Oxygen toxicity remains a major risk factor for the development of CLD and as a consequence the antioxidant status of CLD babies is a major focus of interest. In the present study, we determined whether ascorbate, urate, and total glutathione concentrations were decreased in infants who developed CLD when compared to those who did not. From 34 preterm infants, 141 serial bronchoalveolar lavage fluid (BALF) and plasma samples were collected: 12 developed CLD (median gestation 26 weeks, range 23-28 weeks, median birth weight 780 g, range 630-1070 g), 16 developed and recovered from respiratory distress syndrome (RDS) (median gestation 31 weeks, range 26-39 weeks, median birth weight 1820 g, range 840-4160 g), and six were ventilated for non-respiratory reasons, (median gestation 35 weeks, range 32-38 weeks, median birth weight 2180 g, range 1100-2860 g). Following birth, the concentration of BALF ascorbate, urate and glutathione decreased over the 1st week in all three groups. Thereafter, BALF ascorbate increased in RDS and control infants during the 2nd week but this increase was delayed by 2 weeks in the CLD infants. No differences were noted between the RDS and CLD groups for urate and total glutathione in BALF or urate in plasma. BALF protein concentration was similar in all three groups except for a rise at day 7 in the CLD group but this did not reach statistical significance. Conclusion. A delayed increase in bronchoalveolar lavage fluid ascorbate concentration might be associated with an increased risk of developing chronic lung disease of prematurity.