The high number of cord blood (CB) hematopoietic progenitors made possible CB transplantation in children with hematologic diseases. We collected and cryopreserved CB from siblings of 11 hematologic pediatric patients for possible transplant. The number of BFU-E+CFU-GEMM and CFU-GM was adequate for engraftment. However the possibility of CB transplantation in adolescents and adults is limited by the amount of CB that can be collected. We studied the possibility of expanding the pool of CB hematopoietic progenitors by preincubation of CB CD 34+ cells with several cytokines. After pre-exposition to rhIL-3, IL-1 beta, rIL-6, GM-CSF and stem cell factor (SCF) and cloning with SCF the number of hematopoietic progenitors increased 14-18 fold compared to basal values.