Immune thrombocytopenic purpura (ITP) is either a transient or a chronic bleeding disorder characterized by an unbalanced immune response due to inflammation (ie, infection, autoimmunity). There is new evidence arguing for an immune-mediated mechanism operative in ITP-increased HLA-DR expression, defects in cellular and humoral immunity, and specific autoantibody production. Moreover, different forms of ITP may be associated with specific alterations in the immune response. New immunosupportive modalities emphasize biologic interventions as a therapeutic strategy for autoimmune disorders. Practical guidelines for the diagnosis and treatment of ITP were recently established by the American Society of Hematology. These recommendations will substantially influence patient care and future research.