Intravenous immunoglobulin is not only a very dramatic clinical therapy but also extremely interesting from the point of view of understanding its mechanism of action. The difficulty of delivery and especially the high cost of therapy limits its application; yet it appears to be equal to or perhaps slightly more effective than corticosteroids as a treatment of ITP and is less toxic with prolonged use. The appropriate place for its exact usage remains to be determined, and further controlled trials are urgently needed. Existing studies on its mechanisms of actions are very interesting and have furthered our understanding of the pathophysiology of ITP. Although future work may lead to further applications, initial enthusiasm for the use of IVGG in other autoimmune diseases has been limited by subsequent clinical experience.