Background: Reduced harvest volumes in pediatric donors appear to have the potential to reduce donor-associated risks while maintaining engraftment in recipients; however, the allowable harvest volume reduction remains undefined. Methods: We retrospectively analyzed the data pairs of 553 bone marrow (BM) harvests from pediatric (age at harvest ＜18 yr) sibling donors and clinical outcomes of 553 pediatric (age at infusion ＜14 yr) transplant-naïve recipients to assess the optimal BM harvest volume needed from pediatric donors to obtain the desired CD34+ cell count (≥3.0×10 6 cells per kg of recipient weight), and to study its impact on the clinical outcomes of transplantation in pediatric recipients. Results: The minimum desired CD34+ cell count of ≥3.0×10 6 per kg of recipient weight was achieved for 506 (95.3%) of donor-recipient pairs. The median CD34+ cell yield was 6.4×10 6 per kg of recipient weight (range, 1.2‒33.8×10 6 ) in donors younger than 5 years old at harvest, 4.7×10 6 (range, 0.3‒28.5×10 6 ) in donors aged 5‒10 years and 2.1×10 6 range, 0.3‒11.3×10 6 ) in donors older than 10 years (P ＜0.001). Conclusion The infused CD34+ cell dose (×10 6 cells/kg of recipient weight) had no impact on GRFS; however, a CD34+ cell dose of ＞7×10 6 cells/kg of recipient weight did not improve hematopoietic recovery