Abstract. OBJECTIVE: To examine rates, trends, predictive risk factors, and outcomes associated with pneumothorax in neonates. STUDY DESIGN: Retrospective analyses were used to estimate rates and assess trends in pneumothorax among early preterm (GA <32 weeks), moderate-late preterm (GA 32–36), and term (GA ≥37 weeks) neonates admitted to neonatal intensive care units (NICUs) participating in the Canadian Neonatal NetworkTM from 2005 to 2011. For each GA group, multivariable logistic regression models were derived to predict pneumothorax using risk factors with known clinical relevance. Additional logistic regression analyses assessed associations between pneumothorax and mortality, bronchopulmonary dysplasia, and intraventricular hemorrhage. RESULTS: The study included 71,237 neonates; of them 16,985 (24%) early preterm, 27,709 (39%) moderate-late preterm, and 26,543 (37%) term neonates. The overall rate of pneumothorax by GA was bimodal with estimates of 4.0%, 2.6%, and 6.7% respectively. No significant temporal trends were detected. Risk factors for pneumothorax included: a) for the overall lpopulation- Score for Neonatal Acute Physiology, version II >20, surfactant use, and respiratory distress syndrome; b) for early preterm infants-chorioamnionitis; c) for moderate-late preterm infants-higher birth weight, male sex, rupture of membranes >24 hours, and outborn status; and d) for term infants- male sex, outborn status, and meconium aspiration in term neonates. In early preterm neonates, pneumothorax was associated with mortality, bronchopulmonary dysplasia, severe intraventricular hemorrhage, and prolonged NICU stay. CONCLUSIONS: Pneumothorax rates were higher among term and early preterm neonates admitted to the NICU. Predictors of pneumothorax varied between GA groups. Pneumothorax-associated mortality and morbidity were significantly greater in early preterm infants.