Hyperleukocytosis in patients with leukemia is associated with early mortality, especially due to the pulmonary and neurological complications of leukostasis. The prompt use of leukapheresis may improve patients' survival in the initial treatment period. The medical records of all previously untreated acute leukemia patients were reviewed to determine whether there was hyperleukocytosis at presentation. This study summarizes a single-center experience of leukapheresis that was applied to 12 children with acute leukemia and hyperleukocytosis. The median leukocyte count at diagnosis was 589,000/mm(3) (range: 389,000-942,000/mm(3)) for ALL patients and 232,000/mm(3) (range: 200,000-282,000/mm(3)) for AML patients. A central venous catheter (CVC) was inserted, and leukapheresis procedures were repeated at 12-hour intervals. A total of 29 leukapheresis cycles were performed on 12 children. The median number of cycles of leukapheresis required by each patient was two (range: 1-4). The median absolute and percentage reductions in white blood cell (WBC) count after the first cycle of leukapheresis were 113,000/mm(3) (range: 55,000-442,000/mm(3)) and 36% (range: 16-57.4%), respectively. As a laboratory finding, mild hypocalcemia was the most frequently observed complication. No patients developed any other problem related to the procedure. Our results showed that leukapheresis is a safe and effective procedure if performed by experienced staff.