PURPOSE: Meconium aspiration syndrome is an important cause of neonatal morbidity and mortality, and sometimes patients need mechanical ventilator therapy. The aim of this study was to identify the risk factors which required mechanical ventilation. METHODS: We retrospectively analyzed 44 infants diagnosed as meconium aspiration syndrome from January 2009 to December 2013. We divided into 2 groups (ventilator group and oxygen therapy group) and analyzed the clinical characteristics, vital signs, laboratory findings and clinical courses. RESULTS: Ventilator group and oxygen therapy group included each 22 infants, and there were no significant differences in clinical characteristics between two groups. Time to transfer and time to start oxygen therapy were longer in ventilator group but not statistical difference. Initial mean blood pressure and pH were significantly lower in ventilator group than in oxygen therapy group (P=0.026, P=0.003). Ventilator group had longer treatment period and worse prognosis than oxygen therapy group. CONCLUSION: If the infants with meconium aspiration and respiratory distress represent low pH and hypotension, we have to pay close attention to early oxygen supplementation and proper treatment to prevent poor clinical course.