Large volume leukapheresis (LVL) defined as the processing of greater than three volumes of blood in a single session for peripheral blood stem cell (PBSC) collection was performed in 27 children, aged from 1 to 15 years, with various malignancies. Harvesting of PBSC was started after 4 days of cytokine (G-CSF 12 micrograms/kg s.c.) alone. With the exception of two cases the rest (92.5%) needed only a single apheresis to yield the minimum number of cells required for transplantation. No consistent side-effects were observed and the LVL were well tolerated by children. An average of 7.6 x 10(8) MNC/kg, 6.1 x 10(6)/kg CD34+ and 2.1 x 10(4)/kg CFU-GM were harvested. To date, 19 patients have been transplanted after myeloablative treatment and sustained engraftment was achieved in all cases. LVL can be safely and easily performed in children allowing adequate PBSC collection for transplantation with prompt hematological engraftment.