The hematological recovery of 11 patients who received autologous peripheral blood stem cell transplantation (PBSCT) followed by recombinant granulocyte colony-stimulating factor (rG-CSF) was studied. After high-dose cytarabine therapy or high-dose etoposide therapy followed by rG-CSF, the peripheral blood stem cells were collected using CS-3000 during bone marrow recovery and subsequently cryopreserved in 8 patients with malignant lymphoma, 2 with multiple myeloma and 1 with ALL. The infused dose of CFU-GM following myeloablative chemotherapy ranged from 1.9 to 18.1 x 10(5)/kg BW. Nine patients received more than 5 x 10(5) CFU-GM/kg BW. The median time to reach 1,000 WBC/microliter, 500 neutrophils/microliter, 5 x 10(4) platelets/microliter and 1% reticulocytes was 9 (range; 8-12), 9 (range; 8-12), 16 (range; 8-27) and 15 (range; 9-38) days, respectively. A negative correlation was found between the logarithm of CFU-GM/kg BW numbers infused and the time post-transplant to reach 500 neutrophils/microliter (r = -0.82, P < 0.005), 5 x 10(4) platelets/microliter (r = -0.48) and 1% reticulocytes (r = -0.57, p < 0.05). Transient decrease in the neutrophil (n = 3) or platelet counts (n = 9) was observed 4 to 8 weeks after transplantation, but the recovery of hematopoiesis became stable thereafter. We concluded that with combined use of rG-CSF, the minimal CFU-GM dose required for safe PBSCT is 2 x 10(5)/kg BW.