• Bone marrow examination is widely accepted among pediatric hematologists as a mandatory investigation in childhood idiopathic thrombocytopenic purpura (ITP). The aim of this procedure is to confirm the presence of megakeryocytes and to exclude other conditions, such as leukemia and aplastic anemia. To assess the need for bone marrow examination, we reviewed the charts of 127 children with presumed ITP and found that bone marrow examination led to a different diagnosis in five (3.9%) of them. All five patients had presented with clinical and/or laboratory features atypical of acute ITP; none had leukemia. The initial clinical and laboratory findings of 50 patients with aplastic anemia also were reviewed; all had features atypical of acute ITP. Proper history and physical examination as well as a complete blood cell count are reliable means of recognizing patients with typical vs atypical features of ITP. Bone marrow aspiration could be limited safely to those patients with atypical features of ITP or to patients being treated with corticosteroids.