Twelve patients with idiopathic thrombocytopenic purpura (ITP) who were resistant to conventional steroid therapy under went partial splenic embolization (PSE). PSE was effective for 7 out of 10 eligible cases. The reduction ratio of PAIgG was significantly higher in effective cases. The PAIgG level before treatment and platelet counts one week after PSE were higher in effective cases than those of non-effective cases. The effects of PSE did not depent on age, sex, the duration of disease, platelet count, embolization rate or the effect of intravenous immunoglobulin therapy. No serious side effects were observed. PSE can be an alternative therapy to splenectomy for ITP.