BACKGROUND: The purpose of this study is to evaluate the decreased neutrophil count after the administration of high-dose intravenous immunoglobulin (IVIG) or anti-D immunoglobulin (anti-D Ig) to children with acute immune thrombocytopenic purpura (ITP). In addition, post-treatment changes in absolute neutrophil count (ANC) were also analyzed according to patient age. METHODS: We retrospectively performed a chart review of 83 patients who had received IVIG or anti-D Ig to manage the decreased platelet count due to acute ITP. Pre- and post-treatment ANC were analyzed in the IVIG treatment group and anti-D Ig treatment group, and ANC were compared between each group. In addition, all the subjects were divided into two groups according to age: infantile group and other group, and ANC of these two groups were compared. RESULTS: A decrease in ANC in just a day and recovering to its pre-treatment value on the 7th post-treatment day was observed for the IVIG treatment group. Especially, the decrease in ANC observed in the infantile group was found to recover in 14 days, where-as ANC recovery in the other group was seen within 2 days after the treatment. There was no statistically significant decrease in ANC in the anti-D Ig treatment group. CONCLUSION: IVIG used for childhood acute ITP caused a decrease in ANC more severely than with the administration of anti-D Ig. Subjects aged less than 12 months who were treated with IVIG for acute ITP showed more ANC decrease and needed longer time to recover normal ANC compared to those over 12 months of age.