Thrombopoietin (TPO), which is the main regulator of megakaryo/thrombopoiesis, has been recently cloned and purified, and shown to be useful in discriminating thrombocytopenia due to decreased production or increased platelet destruction. However, there are no detailed investigations about the drug effects on TPO levels during childhood. This study was conducted to measure the TPO levels of children with immune thrombocytopenic purpura (ITP) during steroid and immunoglobulin treatment. Twelve patients with acute ITP were treated with high-dose methyl prednisolone and five patients were treated with intravenous immunoglobulin. Neither steroids nor immunoglobulin were found to have any effect on TPO levels. Blood Coag Fibrinol 11:121-125 (C) 2000 Lippincott Williams & Wilkins.