With the ever increasing number of autologous transplantations of haematopoietic p rogenitor cells the problem of collection of these grafts becomes more urgent. Because up to a certain limit the rate of incorporation correlates with the amount of transplanted progenitors, attempts are made to obtain grafts with a sufficient number of progenitor cells. Under normal conditions blood contrains only a very small amount of progenitor cells. Therefore they must be mobilized before blood sampling which is the most critical moment for obtaining an adequate graft. At the Department of paediatric oncology mobilization is made most frequently by administration of G-CSF, 10 mg/kg per day, either after chemotherapy or separately. In patients where a poorer effect of mobilization is assumed, either larger doses of G-CSF are administered or G-CSF and GM-CSF are combined. If collection of the graft fails, the subsequent procedure depends on the cause. After unsuccessful mobilization and separation there are the following possibilities: 1. new mobilization and separation after another series of chemotherapy, 2. new mobilization with a larger dose of G-CSF or a combination of G-CSF and GM-CSF and subsequent largevolume apheresis, 3. bone marrow sampling, 4. to abandon megachemotherapy with autologous transplantation and select another therapeutic plan.

        Key words: mobilization and collection of peripheral progenitor cells, autologous transplantation of peripheral progenitor cells in children, large volume separations in children