We describe a patient with iron-deficiency anemia, thrombocytopenia and paucity of marrow megakaryocytes, in whom the anemia and the thrombocytopenia responded to the administration of iron. Thrombocytopenia recurred, despite maintenance of normal hemoglobin and iron levels and adequate marrow megakaryocytes. Corticoste-roids and splenectomy were required for the control of the thrombocytopenia. In this patient, the initial manifestations of idiopathic thrombocytopenic purpura were modified by the presence of severe iron deficiency. This case strengthens the contention that iron is essential for megakaryopoiesis and thrombopoiesis.