Aim: Acute leukemia may present with extremely high blast counts (>100 000 /mm3). Leukapheresis effectively reduces the blast count in many patients and is routinely used for immediate leukocytoreduction in adult patients. But this procedure is expensive, requires prompt readiness of specialized blood bank personal. Additional measures such as extracorporeal fluid calculation and priming is required in young patients. In this study linear peristaltic infusion pump was used for exchange transfusion in pediatric leukemia patients with hyperleukocytosis. Material and Method: The blood withdrawn by the pump from the patient was replaced with the same amount of appropriate blood product in order to maintain the isovolumetric state of the patient. Results: Eleven patients ranging in age 3 months to 12 years with high blast counts were enrolled into the study. Two patients were smaller than 2 years of age, six patients were under 20 kg. The mean exchange time was 33 hours and mean amount of transfused blood was 2382 ml. Their mean initial leukocyte count was 393 000/mm3. Their mean end-leukocyte count was 67 982/mm3. No side effects were observed in any of the patients. Conclusion: Exchange transfusion of patients with hyperleukocytosis with the use of linear peristaltic pump, is a safe and cheap method for this group of patients.