The aim of this study was to detect the expression of transforming growth factor-ß1 (TGF-ß1) in neonatal rats with hyperoxia-induced bronchopulmonary dysplasia (BPD) and to explore its relationship with lung development. Forty-eight rats (2-3 days old) were randomly divided into a hyperoxia group and a control group (N = 24) which were then fed in ≥95% oxygen atmosphere and air, respectively. On the 1st, 3rd and 7th days of hyperoxia exposure, morphological changes of lung tissues were observed under an optical microscope. TGF-ß1 mRNA and protein levels in lung tissues were detected by real-time quantitative polymerase chain reaction and western blot, respectively. With increasing time of hyperoxia exposure, the hyperoxia group gradually suffered from pathological changes such as poor development of lung tissues, alveolar simplification, decrease in the number of alveoli, and hindered pulmonary microvascular development. On the 7th day of hyperoxia exposure, TGF-ß1 mRNA and protein levels (relative to b-actin) of the hyperoxia group (0.34 ± 0.19 and 0.21 ± 0.09, respectively) were significantly lower than those of the control group (0.83 ± 0.45 and 0.57 ± 0.45, respectively; P < 0.05). TGF-ß1 participates in the pathogenesis of BPD as an important regulatory factor during pulmonary vascular development.