Background Extreme leukocytosis, generally defined as a white blood cell (WBC) count of more than 100 × 109/L consisting largely of blast cells, especially when accompanied by clinical signs and symptoms of leukostasis or hyperviscosity, often predicts a poor clinical outcome in patients with acute leukemia. In this study, we aimed to investigate the effect of volume replacement (VR) during therapeutic leukapheresis (TA) procedure on early mortality rate and WBC reduction. Study Design and Methods We retrospectively analyzed 29 patients who underwent TA from 2007 to 2011. Fifteen of the patients underwent TA procedure with VR and 14 of the patients underwent TA procedure without VR. Results WBC reduction was significantly higher in patients who underwent TA with VR (p < 0.001). Early mortality rate was significantly lower in leukemia patients who underwent TA with VR than in patients who underwent TA without VR (p < 0.01); early mortality rates were 6.7% for 7-day and 13.8% for 100-day survivals. The mortality rates in the TA without VR group, however, were 42.9 and 71.4% for 7- and 100-day survivals, respectively. Conclusion Decreased early mortality rate in TA with VR group may be associated with prompt reduction of WBCs achieved with TA with VR and may also be associated with removal of the cytokines related to leukostasis. TA with VR would give more time for induction chemotherapy and increased overall survival rate. © 2013 American Association of Blood Banks.