The objective of this study was to determine if newborn premature infants with severe respiratory distress syndrome (RDS) who developed bronchopulmonary dysplasia (BPD) demonstrate, within the first 3 days of life, lower blood levels of antioxidants and higher urine levels of lipid peroxidation products than premature infants who recovered from RDS. Perinatal variables (gestational age, birth weight, and Apgar scores) and antioxidant indices in cord and in third day of life plasma and red blood cell (RBC) samples from healthy premature infants (n = 35), infants with RDS (n = 23) and infants with BPD (n = 23) were examined. Antioxidant indices included selenium, alpha-tocopherol, total and oxidized glutathione, glutathione peroxidase, superoxide dismutase, and urinary malondialdehyde. By inferential statistics, only the perinatal variables and cord plasma selenium distinguished healthy premature infants from premature infants with RDS or BPD. From perinatal variables and antioxidant indices we calculated: (1) cord to third-day-of-life variable differences, (2) variable-to-variable ratios, and (3) ratios of a difference for one variable to a difference for any second variable. Subset regression analysis yielded an equation (adjusted R2 = 0.8839) that correctly predicted infants who developed BPD 100% of the time. Predictor variables for BPD were gestational age, Apgar at 1 min, cord and third-day-of-life RBC selenium, cord total glutathione, cord and third-day-of-life glutathione peroxidase and nine different ratios involving Apgar scores, RBC selenium, total and oxidized glutathione, alpha-tocopherol, glutathione peroxidase, and superoxide dismutase. In this study, there was no relationship between lipid peroxidation and BPD. There was a higher rate of patent ductus arteriosus, congestive heart failure, and retinopathy of prematurity in infants with BPD. This study confirms that low plasma selenium and alpha-tocopherol levels in premature infants (< or = 30 weeks' gestational age or lower) were significantly associated with an increased respiratory morbidity.