Acute myelomonocytic leukemia (AML) is a malignant-hematopoetic clonal disease of bone marrow and impaired production of normal blood cells. The leukemic cell infiltration may be companied by anemia and thrombocytopenia. Oral manifestations of the disease are gingival ulcerations, mucositis, gingival bleeding and gingival enlargement. A 47-year-old-man with AML-M4 referred to periodontology clinic for treatment of gingival hyperplasia and bleeding. At the second appointment, diffuse gingival ulcerations were seen. Two teeth were extracted under antibiotic prophylaxis. Gingival specimens were sent to pathology. Histochemical/immunohistochemical analysis showed AML His medical therapy continued with chemotherapy and allogeneic bone marrow transplantation. He died 9 months after initial diagnosis.