The indications for bone marrow examination in children are varied and complex. In children who have isolated anemia, marrow examination usually is limited to those who have severe or persistent normocytic anemia in the absence of blood loss or hemolysis. Bone marrow studies are not necessary in children who have reactive lymphocytes; in most children who have leukopenia, leukocytosis, or thrombocytosis; and in many who have ITP. Marrow examination always is indicated when leukemia is suspected, in children who have pancytopenia of unknown etiology, and when metastatic involvement of the marrow is suspected. If one believes that examination of the bone marrow may be indicated, consultation with a pediatric hematologist/oncologist is recommended. The consultant can verify the need for the examination, decide what specific marrow studies should be performed, and suggest what other laboratory studies could be helpful.