The main goal of this study was to assess the cytological evaluation of tracheal aspirate, in order to predict the early diagnosis of bronchopulmonary dysplasia (BPD) in high-risk babies during mechanical ventilation. Method: Samples from 43 infants (aged < 34 weeks and weighed ≤ 1500 g) were examined cytologically; who were admitted to Pediatric Intensive Care Units and diagnosed as respiratory distress syndrome by clinical and radiological criteria. Results: Up to 150 tracheal aspirates from 43 infants were examined to demonstrate cytological changes in bronchial epithelial cells that progressed to dysplasia. It was cytologically designated Class III. According to cytological criteria, all intubated infants had reactive hyperplastic and metaplastic epithelial changes. There were dysplastic changes in 23 out of 33 who developed BPD and 7 out of 40 who had a normal outcome. The variation between the numbers of neonates that had dysplasia in the BPD and the non-BPD group was significant (P < 0.002 by chi-square test). Conclusion: In order to monitor the development of lung injury and repair, tracheal aspirate cytology is simple, non-invasive and fast. Cytological monitoring of respiratory distress infants may be helpful in the early diagnosis and prognosis of the developing BPD. Evaluating new BPD preventive treatment schemes may also be valuable.