We report a case of isolated extramedullary relapse of acute myelogenous leukemia in a tooth following bone marrow transplantation. The patient was a 4-yr-old child who developed gingival swelling and bleeding while in bone marrow remission. Crush artifact prevented definitive diagnosis of leukemic relapse in a biopsy of the gingival soft tissue, but decalcification of the tooth showed an unequivocal leukemic infiltrate in the dental pulp. Decalcification and sectioning of extracted teeth are recommended when equivocal findings are present in the gingival soft tissue or when there is a history of lymphoreticular malignancy.