The intraoral occurrence of granulocytic sarcoma is extremely rare. This article describes 2 cases of granulocytic sarcoma of the gingiva in different clinical situations: one as a precursor to acute myeloid leukemia in a 50-year-old man and the other as a sign of blast crisis in a 59-year-old man with chronic myelomonocytic leukemia. Clinicians and oral surgeons should consider the possibility of tumorous lesion and systemic disease when an intractable ulcer is encountered in an oral cavity. Early diagnosis may improve prognosis and increase expectancy of survival. Keywords: acute myeloid leukemia, chloroma, chronic myelomonocytic leukemia, extramedullary myeloid tumor, gingiva, granulocytic sarcoma, ulcer