To determine the incidence of bronchopulmonary dysplasia, to identify maternal and neonatal factors associated with the disease, and to determine the correlation between bronchopulmonary dysplasia and the progress of newborns. Data were prospectively collected on 153 infants born in Campinas (state of São Paulo, Brazil) from September 2000 to April 2002 weighing less than 1,500 g and treated at the University Hospital. The ratio of incidence rates with 95% CI, Breslow-Cox regression, Student's t test, linear regression and the Fishers exact test were utilized. Among the 124 babies who survived until 28 days of age, 33 (26.6%) developed bronchopulmonary dysplasia. Birthweight < or = 1,000 g (5.6; 95% CI 3.0, 10.4) and gestational age < or = 30 weeks (4.0; 95% CI 2.1, 7.2) were correlated with increased incidence of bronchopulmonary dysplasia. Breslow-Cox regression showed that other factors including gender, Apgar score, hyaline membrane disease, antenatal steroid therapy, pregnancy-induced hypertension, delivery route and maternal age were not associated with bronchopulmonary dysplasia. Mean duration of hospitalization and ventilator therapy in newborns with and without bronchopulmonary dysplasia was 78.8 days (SD = 26.67) vs. 43.0 days (SD = 14.49) (p < 0.01) and 27.2 days (SD = 21.26) vs. 3.7 days (SD = 3.02) (p < 0.01), respectively. Mean weight gain per day was lower in newborns with bronchopulmonary dysplasia (p < 0.01). Mortality in newborns with bronchopulmonary dysplasia was 21% (p < 0.00005). Gestational age and birthweight were inversely proportional to incidence of bronchopulmonary dysplasia. After the onset of bronchopulmonary dysplasia, newborns with the disorder required longer periods of ventilator therapy and hospitalization, and presented inadequate weight gain and higher mortality rates than newborns without bronchopulmonary dysplasia.79550-6