Sixteen patients presenting with granulocytic sarcoma without evidence of acute leukemia were seen and diagnosed at The University of Texas M.D. Anderson Hospital and Tumor Institute at Houston from 1962 to 1985. Seven of them (44%) did not develop acute leukemia. Of these seven, four are alive with no evidence of disease 3.5 to 16 years after initial presentation; the remaining three patients died of their disease within 2 to 8 months of presentation. Two of 16 patients were diagnosed within the last 15 months and do not have adequate follow-up. The seven remaining patients developed acute leukemia within 1 week to 13 months of the diagnosis of granulocytic sarcoma. Six of them died 5 weeks to 16 months after diagnosis; one patient has been in complete remission for 8 years. Twelve of these 16 cases (75%) were initially misdiagnosed, most frequently as large cell lymphoma. The remaining four cases were correctly diagnosed as granulocytic sarcoma. The naphthol-ASD-chloroacetate esterase stain was required to make the correct diagnosis in all cases. Contrary to findings in other series, granulocytic sarcoma arising in nonleukemic patients does not necessarily progress to acute leukemia. At least four of 16 (25%) patients in this series did not develop acute leukemia during the 3.5 to 16 years they have been followed. No prognostic factors were identified in this series to predict which patients would develop acute leukemia and which ones would not.