Hematopoietic recovery kinetics was evaluated in five children with therapy-refractory cancers who received peripheral blood stem cell autotransplantation (PBSCT) following marrow-ablative chemotherapy. Four children received graft containing more than 1.5 X 10(4) CFU-GM/kg and days required to achieve granulocyte counts of greater than 0.5 X 10(9)/l were 6, 10, 13, and 18, respectively. One patient received 0.9 X 10(4) CFU-GM/kg, but, recovery of granulopoiesis was retarded (greater than 30 days). The days required to achieve platelet count of greater than 50 X 10(9)/l were 12, 15, 16, 195, and greater than 240, respectively. Transient decrease of blood cell counts developed 3 to 5 weeks after transplantation and thereafter, the recovery of hematopoiesis became stable. With the use of a large number of progenitors, PBSCT seems to be safe and effective new type of stem cell rescue operation as an alternative to bone marrow transplantation.