This patient, 30 year-old korean male, was admitted with complaints of the gingival enlargement and spontaneous bleeding of the gingival tissue with acute leukemia. In reviewing this case, the following points should have been understood; 1. This is a case of the gingivitis, gingival enlargement, gingival bleeding, so the patient showed the masticatory disturbances. 2. The generalized weakness, petechia in skin, anemia, and hepatomegaly on palpation were seen. 3. With the histopathological examination by means of microscopic views, numerous myelocytic cells, of which their shapes were in irregular, were appeared. 4. The prognosis was poor in spite of any other internal treatments.