To asses the role of pulmonary inflammation in the outcome of preterm neonates with respiratory distress syndrome (RDS) we measured soluble intercellular adhesion molecule-1 (ICAM-1), interleukin-8 (IL-8), eosinophil cationic protein (ECP) and transforming growth factor beta-1 (TGF beta 1) in tracheobronquial lavage (TBL) fluid of 15 preterm infants; 9/15 completely recovered from RDS and 6/15 developed chronic lung disease (CLD). ICAM-1 (p: 0.001) and TGF beta 1 (p: 0.04) levels increased in TBL fluid during the first days of life. The values of ICAM-1 were correlated to the days of 0(2) and mechanical ventilation dependency. At 3 days of age, ICAM-1 levels in TBL fluid were higher in infants who later developed CLD compared to infants without CLD (24.5 vs 8.3 micrograms/ml; p: 0.02). Thereafter no significant differences were found although the CLD group had higher values. IL-8 levels showed a fall, specially from 1 to 3 days of age in children without CLD (77.0 to 41.7 ng/ml) although not significant. No difference in TGF beta 1 values were found between both groups, but the TGF beta 1 levels were lower in patients with CLD and they showed undetectable values in 8 samples. ICAM-1 is a major factor associated with airways inflammation whereas IL-8 is not a good marker during the first days of life to predict the RDS outcome. A defect of TGF beta 1 in the smallest premature infants may delay the lung repair process which occurs after tissue injury. High ICAM-1 levels and low TGF beta 1 levels in lung fluid are related to oxygen dependency at 28 days of age.