OBJECTIVE The purpose of this study was to compare the efficacy and side effects of intravenous immunoglobulin (IVIG) with intravenous anti-D immunoglobulin for treatment of newly diagnosed acute childhood Idiopathic thrombocytopenic purpura (ITP). METHODS Children (6 months to 14 years) with newly diagnosed acute ITP and platelet count below 20,000/ microL were randomized to receive single dose intravenous 75 microg/kg anti-D or 1g/kg IVIG for two consecutive days (total dose 2 g/kg). Response rate defined as a platelet count over 20,000 / microL 72 hours after initial treatment. RESULTS Eighty one patients (52 male and 29 female) with mean age of 5 years and 3 months randomly divided in anti-D group (n=42) and IVIG group (n=39). Mean baseline (pretreatment) platelet counts were 15406 / microL and 15230/ microL in anti-D and IVIG group, respectively. The response rate in IVIG group (98%) was more significant than anti-D group (76%); (P = 0.017). After 7 days the platelet counts of all patients in IVIG group were more than 20,000/ microL while in anti-D group 12% had platelet counts below 20,000/ microL. CONCLUSIONS In acute childhood ITP, initial treatment with IVIG (2g/Kg in divided dose) increased platelet count more rapidly and more significant than intravenous anti-D (single dose of 75 microg/kg) within the first 72 hours.