To know the clinical characteristics and the prognostic factors of hyperleukocytic acute leukemia, we reviewed 244 patients with acute leukemia associated with hyperleukocytosis. Restrospective analysis and control study were used. Hyperleukocytosis occured in 8.5% of patients with acute leukemia. Hyperleukocytosis in ALL was more common than that in AML. Among AML with hyperleukocytosis, M5 subtype was the most. Hepatomegaly, splenomegaly, lymphadenopathy, DIC and CNSL were more frequent in hyperleukocytosis group. The complete remission rate was 41.4% for patients with hyperleukocytosis versus 54.2% for patients with non-hyperleukocytosis. The early mortality rate was significantly increased in hyperleukocytic patients (23.8%) as compared to the nonhyperleukocytic group (11.1%). Intracranial hemorrhage was the main cause of early death. The high risk factors of early death were: hemoglobin < or = 40 g/L, blood platelet < or = 30 x 10(9)/L, DIC, infection, CNSL at presentation. Acute leukemia with hyperleukocytosis has poor prognosis. Especially, acute myeloid leukemia with hyperleukocytosis must be taken seriously because of high early mortality rate.