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Background: The optimal cryopreservation cell concentration during the peripheral blood stem cell (PBSC) collection is a controversial topic. We evaluated the influence of cryopreservation concentration on the recovery of hematopoietic progenitor cells and the kinetics of hematopoietic recovery of autologous stem cell transplant patients., Study Design and Methods: In this retrospective study, we compared two different cryopreservation protocols: 1×10(8) cells/mL (Protocol A) and 2×10(8) cells/mL (Protocol B). A total of 419 PBSCs were analyzed with regard to the number of viable cells and colony-forming units-granulocytes-monocytes (CFU-GM) progenitors. The hematopoietic recovery of 275 patients who received PBSCs cryopreserved at a dose of 1×10(8) cells/mL (Group A) and 2×10(8) cells/mL (Group B) were compared., Results: There were no significant differences in recovery of viable cells between Protocol A and Protocol B. The median of recovery of CFU-GM progenitors was significantly higher in Protocol B (41.2 vs. 57.3, p<0.01). The median times to neutrophil recovery (≥500×10(6) /L) and platelet (PLT) recovery (≥20×10(9) /L) in Groups A and B were 11 days versus 11 days and 12 days versus 12 days, respectively. However, by Kaplan and Meier analyses, Group B recovered neutrophils with a little delay (p=0.01). No difference was observed with regard to time to PLT recovery. On multivariate analysis, we found that the number of CD34+ cells and CFU-GM progenitors had a significant influence on hematopoietic recovery., Conclusion: Cryopreservation of PBSCs at a dose of 2×10(8) cells/mL did not affect the recovery rate of viable cells or the hematopoietic recovery of autologous stem cell transplant patients., (© 2010 American Association of Blood Banks.)