Idiopathic thrombocytopenic purpura (ITP) is a bleeding disorder in patients who are otherwise healthy and present with thrombocytopenia with normal red cells and leukocytes. ITP is a diagnosis of exclusion and is in origin heterogeneous. The unknown etiology and the lack of clinical data from controlled prospective studies are reasons for controversies in diagnosis and management. Study endpoints traditionally include the velocity of platelet increase after drug intervention or observation, although a rapid elevation of the platelet count is of questionable clinical value. Evaluation of other endpoints is needed.