In total, 18 of 26 double high-dose chemotherapies (HDCT) in pediatric solid tumors were rescued with peripheral blood stem cells collected during a single leukapheresis round (single-harvest group, SHG). In the remaining eight HDCT, additional leukapheresis were necessary after the first HDCT (HDCT1) to rescue the second HDCT (HDCT2) (double-harvest group, DHG). Stem cell collection after HDCT1 was inefficient and delayed in patients who had received prior chemotherapy before HDCT1. The interval between HDCT1 and HDCT2 was shorter in SHG than in DHG (median 62.5 days vs 178.5 days, P-value=0.002). Hematologic recovery in HDCT2 was delayed compared to HDCT1. However, there was no difference in hematologic recovery between SHG and DHG. A high rate of treatment-related mortality (TRM) was recorded during HDCT2, but there was no evidence that the shorter interval caused a higher rate of TRM (P-value=0.454). The probability of disease-free survival at 2 years after HDCT2 in the SHG and DHG were 66.7 and 25.0%, respectively (P-value=0.031). Therefore, to administer the second HDCT earlier in double HDCT, and thus to improve the survival of patients with high-risk solid tumors, the single-harvest approach is recommended rather than the double-harvest approach.