Objectives: To determine if tracheal lavage concentrations of the transcriptio n factor NF-κB, which is activated by risk factors associated with bronchopulm onary dysplasia (BPD) and induces expression of cytokines associated with BPD, i s related to BPD in premature infants. Design: Serial tracheal lavage samples fr om intubated premature infants were analysed for cell count and concentrations o f interleukin (IL)8 and NF-κB, corrected for dilution by secretory component concentrations. Setting: Level III university hospital neonatal intensive care un it. Patients: Thirty three intubated infants (mean (SD) birth weight 903 (258) g, median gestation 27 weeks (range 24-31)-) in the first 14 days of life. Main outcome measures: Tracheal effluent NF-κB, IL-8, and cell counts, corrected for dilution by secretory component measurement. Results: Square root transforme d NF-κB concentrations were significantly related to signs of inflammation (ce ll count, P = 0.002; IL-8, P = 0.019) and to simultaneous fraction of inspired oxygen in samples from the first 3 days of life (P = 0.512, P < 0.003). Of the 3 2 subjects with samples in the first 3 days of life, the half who either died or had BPD had higher NF-κB concentrations than those without BPD (square root c oncentration 0.097 (0.043) vs 0.062 (0.036) μg/μg protein/μg secretory compon ent, P = 0.018). Conclusions: Tracheobronchial lavage NF-κB concentrations are related to lung inflammation, oxygen exposure, and pulmonary outcome in intubat ed preterm infants. NF-κB activation may be an early critical step leading to BPD. Objectives: To determine if tracheal lavage concentrations of the transcript n factor NF-κB, which is activated by risk factors associated with bronchopulm onary dysplasia (BPD) and induces expression of cytokines associated with BPD, is related to BPD in premature infants. Design: Serial: tracheal lavage samples fr om intubated premature infants were analyzed for cell count and concentrations of interleukin (IL) 8 and NF-κB, corrected for dilution by secretory component concentrations. Settings: Level III university hospital neonatal intensive care un it. Patients: Thirty Three intubated infants (mean (SD) birth weight 903 (258) g, median gestation 27 weeks (range 24-31) -) in the first 14 days of life. Main outcome measures: Tracheal effluent NF-κB, IL- Results: Square root transforme d NF-κB concentrations were significantly related to signs of inflammation (ce ll count, P = 0.002; IL-8, P = 0.019) and Of the 3 2 subjects with samples in the first 3 days of life, the half who either died or had BPD had life (P = 0.512, P <0.003). NF-κB concentrations than those without BPD (0.097) vs 0.062 (0.036) μg / μg protein / μg secretory componets, P = 0.018). Conclusions: Tracheobronchial lavage NF-κB concentrations are related to lung inflammation , oxygen exposure, and pulmonary outcome in intubat ed preterm infants. NF-κB activation may be an early critical step leading to BPD.