Methotrexate is a very potent inhibitor of dihydrofolate reductase and causes bone marrow suppression and megaloblastic anemia. It is widely used in combination with other chemotherapeutic agents in lymphoproliferative disorders. A 63 year old man with ischioneuralgia developed exertional dyspnea and dizziness after he had intentionally taken methotrexate in doses of 5mg per day for 2months. Five months after discontinuation of methotrexate, his bone marrow showed the hypercellular marrow with 90% cellularity, 15% blasts and marked dysgranulopoiesis, suggestive of refractory anemia with excess blasts(RAEB). The hematopoietic cells were not enough aspirated for proper diagnosis in follow up bone marrow after three months. The bone marrow aspirates showed 13% blasts, and marked dysgranulopoiesis. The bone marrow biopsy showed hypercellular marrow with 100% cellularity, but marked fibrosis was developed. The cytogenetic study revealed normal karyotype.