An unusual case of granulocytic sarcoma presenting in a pericardial effusion following trauma and preceding acute myelogenous leukemia (AML) by 8 months is presented. Five additional cases of granulocytic sarcoma preceding leukemia collected by the author are also tabulated. Granulocytic sarcoma in a nonautopsy population of myelogenous leukemic patients was found to be 2.9%. When presenting in an extramedullary site, especially preceding peripheral blood and bone marrow manifestations of leukemia, a misdiagnosis of histiocytic lymphoma may result. In questionable cases, other techniques including the naphthol-ASD-chloroacetate stain, touch imprints, immunoperoxidase stain for lysozyme, and electron microscopy should be utilized. Although only a small series, the most recent cases have shown induction/remission and survival characteristics of AML patients without granulocytic sarcoma.