Objectives : This study was conducted to evaluate the association between first episode polarity of pediatric bipolar disorder and prognosis. Methods : We analyzed the clinical records of 66 inpatient subjects with DSM-IV defined pediatric bipolar disorder. The patients were split into 2 groups according to the polarity of the illness onset [depressive onset (DO) vs. manic/hypomanic/mixed onset (MO)]. Clinical feature and prognosis were compared between the two groups of patients. Results : In our sample, 68% of patients experienced a depressive onset. In DO patients, rates of suicidal attempt, episodic illness course and comorbid disruptive behavior disorder were higher than rates in MO patients. Conclusion : Findings from this study suggest that polarity of illness onset may be useful in predicting the prognosis of pediatric bipolar disorder.