We describe a 45-year-old female who developed acute myelogenous leukemia (AML) associated with a mediastinal mass. The patient achieved a complete remission accompanied by resolution of the mediastinal mass following intensive chemotherapy alone. A review of the literature disclosed ten AML patients with a mediastinal tumor; all five patients who had mediastinal granulocytic sarcoma treated by local irradiation prior to developing AML, eventually relapsed as frank leukemia and died soon afterwards. On the other hand, three of the other five patients who simultaneously developed both a mediastinal tumor and overt AML achieved complete remission with combination chemotherapy. In conclusion, intensive chemotherapy should be considered for a patient with granulocytic sarcoma of the mediastinum, irrespective of the concomitant leukemia.