A 31-year-old female with acute myelocytic leukemia was admitted to our hospital in June 2004. She had complications of brain abscess at the WBC nadir after the second course of induction therapy. However,because the platelet count was low, neurosurgical procedures, including craniotomy/abscess resection, or abscess drainage, were not performed, and we could not detect bacteria or fungus as the cause of brain abscess. Combination therapy with meropenem trihydrate and fosfluconazole was effective. Thereafter, she underwent related peripheral blood stem cell transplantation, and has had no recurrence of brain abscess. Brain abscess during chemotherapy for patients with acute leukemia is commonly due to fungus,particularly Aspergillus, which has a very high fatality rate. Therefore, the treatment of brain abscess without the detection of bacteria and fungus requires combination therapy with antifungal agents and antibiotics. In this case, methionine-positron emission tomography was useful for the evaluation of therapeutic effectiveness for brain abscess.