Introduction: Granulocytic sarcoma (GS) or chloroma is a rare extramedullary manifestation of acute myelocytic leukemia (AML). Its occurrence in the maxillary sinus is extremely rare. Objective: To describe a patient with AML whose initial manifestation was a GS of the left maxillary sinus. Case report: An 18 year-old male was attended in our service in March 1999 presenting sinusitis for forty days, without improvement with the employed treatment. He developed proptosis, diplopia, intense and persistent headache, continuous fever, and left nasal obstruction and epistaxis. Rhinoscopy revealed a green-grayish lesion in left nasal cavity. Computed tomography of the paranasal sinuses revealed compromising of ethmoidal cells and maxillary sinus, associated to bony destruction of the left orbit. Histopathologic study diagnosed granulocytic sarcoma which, associated to blood count and bone marrow aspirate, led to the diagnosis of AML. The patient was submitted to chemotherapy, presenting quick improvement of the signs and symptoms. However, seven days after the treatment, he presented acute abdomen due to appendicitis and, 24 hours after the surgery, he developed septicemia and died. Conclusions: Granulocytic sarcoma of the maxillary sinus is a rare tumor, but its association with AML is frequent and the diagnosis could be difficult in its pre leukemic stage. Prognosis is favorable if an early diagnosis is accomplished.