Granulocytic sarcoma (GS) is a malignant tumour composed of poorly differentiated myeloid cells forming in an extramedullary site. It is generally associated with acute leukaemia, particularly the myelocytic type. Its appearance in patients with chronic myeloid leukaemia is exceptional. GS can appear in multiple locations with the oral cavity being rarely involved. A mandibular GS detected in a patient with chronic myeloid leukaemia 10 days after a tooth extraction is reported. The pathogenesis (by metastatic cells or migration through the Haversian canals) of the tumour is discussed.