A rare case of granulocytic sarcoma of orbit preceding the onset of acute meyloblastic leukaemia is presented. A 7-year-old boy presented with proptosis and no other systemic complaints. The appearance of an enlarged muscle in initial tomographic imaging with a normal peripheral blood picture caused a diagnostic problem. Biopsy suggested a diagnosis of granulocytic sarcoma. Subsequent bone marrow study revealed the diagnosis of acute myeloid leukaemia.