Purpose: Immune thrombocytopenic purpura (ITP) is frequently observed bleeding disorder in children. High dose intravenous immunoglobulin G (IVIG) has been used for treatment of ITP since 1981 by Imbach, and now several methods of IVIG infusion are used. Since 1983, we have treated ITP patients with short-term and low-dose IVIG according to the individual patient\'s response daily. There were no laboratory predictive factors of chronic ITP. Methods: We evaluated 259 childhood acute ITP patients retrospectively who were newly diagnosed at the Department of Pediatrics, Kyungpook National University Hospital from September, 1983 to December, 2012. We analyze the response of treatment and predict of childhood chronic ITP before six months according to the individual response for IVIG treatment. We divided total patients by 2 groups according to the time to reach desired platelet counts (50,000/mm3) after daily treatment of IVIG, rapid (1 or 2 doses) and slow responder (more than 3 doses). We evaluated the time to reach desired platelet counts (50,000/mm3) after treatment of IVIG, relapse rate and progress of chronic ITP. Results: The median age was 4.1 years (1 month ~ 18 years), male to female ratio was 1.6:1 and median follow up duration was 25 months (0.5 month ~ 341 months). Eighty patients (30.9%) were relapsed (less than 50,000) and median interval to relapse was 3.6month (3 days ~ 6 month) after first diagnosis. Thirty nine patients relapsed within 1 month (48.6%) after first diagnosis, 17 patients between 1-2 month (21.3%), 9 patients between 3-4 month (11.3%), 8 patients between 5-6 month (10%) and 7 patients (8.8%) relapsed after 6 month. Among 182 patients followed up over 6 months, 41 patients (22.5%) were eventually diagnosed as chronic ITP. All chronic ITP was observed only in relapse patients. Among 182 patients, 102 patients (56.7%) belong to rapid responder group and 17 patients of them (16.7%) diagnosed chronic ITP. Eighty patients (44.4%) belong to slow responder group and 24 patients of them (30%) diagnosed chronic ITP (p-value: 0.033). In recent data, among 28 patients lesser than 6 months of age 22 patient were followed more than 6 months. And all patients were acute cases. Conclusion: Individual response rate of IVIG treatment and age will be used a predictor of chronic ITP earlier than six months.