Results of collection and transplantation of peripheral blood progenitor cells (PBPC) mobilized by G-CSF in 31 children with different malignancies were analysed. A total of 43 aphereses were performed, following administration of granulocyte colony-stimulating factor (G-CSF), using a continuous flow blood cell separator (Cobe Spectra) through a central venous catheter. For patients weighing <or= 25 kg the extracorporeal line was primed with red blood cells. The mean blood flow rate was 33.2 ml/min (range 12-56 ml/min). The mean number of mononuclear cells (MNC), granulocyte-macrophage colony-forming units (CFU-GM) and CD34+ cells collected were 7.22 x 10(8)/kg body weight (b.w.), 15.9 x 10(4)/kg and 5.44 x 10(6)/kg respectively. The morbidity related to PBPC collection was low and the mean apheresis time was 302.7 min (range 115-492). The volume of processed blood for apheresis (per kilogram body weight) ranged from 117 to 539.6 (mean 309.13 ml/kg). 20 patients required only one apheresis to collect the minimum requirement of 5 - 7 x 10(8)/kg of MNC. All patients subsequently underwent autografting with PBPC after myeloablative therapy. Days to achieve an absolute count of neutrophils (ANC) > 0.5 x 10(9)/l and a platelet count of 20 x 10(9)/l without platelet support were 9.5 and 18, respectively. The number of CD34+ cells infused correlated highly with engraftment kinetics. The extra-medullary toxicity was low and manageable.