Due to the movement of hematopoietic stem cells through the bone marrow environment, it may be possible to effectively harvest peripheral blood stem cells in a second apheresis within a few hours after a first apheresis. In a retrospective analysis, 107 aphereses were performed in consecutive 33 pediatric and six healthy pediatric donors who received granulocyte-colony stimulating factor at 10 microg/kg/day or 400 microg/m(2)/day for five days. The median age and weight of cases were seven yr (range 1-19) and 20 kg (range 8-87). The toxicities related to apheresis procedure were minimal in both aphereses. In 22 double aphereses, the average number of CD34-positive cells per body weight (kg) collected was 5.3 +/- 4.2 (range 0.6-16.6) and 4.7 +/- 3.1 (range 0.2-10.9) x 10(6) in the first and second aphereses, respectively (p = 0.569). Multivariate analysis showed that number of CD34-positive cells collected in the first apheresis (p = 0.008) was an independent factor of increased CD34-positive cells in the second apheresis. Double apheresis in a single day was feasible and this procedure may be able to lessen the burden of apheresis compared to two consecutive-day apheresis.