The AMICUS TM system was recently introduced for peripheral blood stem cell (PBSC) aphereses in adults. We conducted a single center field evaluation to obtain data about the performance of this system in children with a body weight (bw) < 25 kg. Results of blood priming procedures were compared to historical data obtained with the Fenwal CS30001 (CS 3000). From August, 2001 to February, 2007, 47/178 (26%) PBSC aphereses procedures were performed in our institution with the AMICUS TM system in 35 small patients (median bw 13.9 kg; range 6.7-24; age 2.78 years; range 0.97-7.06). The patients suffered from various malignant primary diseases or recurrences. We primed the system with packed RBC in case of >30% dilution of the RBC volume (n 5 31) or with saline (n 5 16). Compared to the CS3000, the AMICUS TM revealed comparable collection efficiencies (CE) for CD34 1 cells (median 67%, range 26-120), lymphocytes (75%, 25-138), monocytes (54%, 23-173), and granulocytes (10%, 1.5-36), MNC (57% 24-125), but a significantly higher erythrocyte and granulocyte, and a lower platelet CE. There was a significant negative correlation between total leukocyte count and CE for MNC (r 5 20.566; P < 0.001) and CD34 1 cells (r 5 20.517; P < 0.001). There was no significant statistical or clinical difference between the CE in blood-primed procedures and saline-primed procedures. With the AMICUS TM we saw statistically less citrate reactions compared to the CS 3000. We conclude that the AMICUS TM system is safe and efficient to harvest PBSC on a routine basis in pediatric patients, even in children 10 kg bw. J. Clin.