Chloroma (leukemic infiltrate or granulocytic sarcoma) is a localized extramedullary mass of immature granulocytic cells. They are uncommon tumors that usually occur in patients with leukemia, mostly of the myeloid type. Involvement in the head and neck region is rare. Granulocytic sarcomas of the face, maxilla, paranasal sinuses, temporal bone, and pharynx have all been documented in the past. We present the first reported case of a granulocytic sarcoma involving the masseteric muscle in an 8-month-old white male diagnosed with acute myeloid leukemia (AML). The lesion resolved with chemotherapy but the patient subsequently died. This case reaffirms the importance of including chloroma in the differential diagnosis of lesions in patients with AML and the prognostic value they hold. Copyright (C) 2000 Elsevier Science Ireland Ltd.