We describe a 3-year-old boy with acute megakaryoblastic leukemia, who experienced isolated mandibular relapse 15 months after first hematological recurrence of the disease treated with allogeneic bone marrow transplantation. Local control of the disease was achieved with radiotherapy combined with chemotherapy. The child is now in continue complete remission 20 months after the mandibular relapse. The patient shows extensive chronic GVHD, that might play a role in the control of the neoplastic disease.