Repeated high-dose chemotherapy (HDC) with stem cell support is advocated for curative treatment of epithelial ovarian cancer patients, requiring large quantities of progenitor cell harvest. Although the switchover to peripheral blood stem cell transplantation has generally made possible the harvest of large quantities of progenitor cells, the minimum threshold is still pertinent for planning the safe conduct of HDC. However, as the minimum threshold for safe peripheral blood stem cell transplantation (PBSCT) is not yet established, this study was designed to clarify the minimum amount of progenitor cells required for prompt recovery of hematopoietic. Retrospective analysis was performed on 52 HDCs administered in 37 ovarian cancer patients. After autologous bone marrow aspiration (10 patients) or peripheral blood stem cell harvest (27 patients), colony-forming unit granulocyte macrophage (CFU-GM) were enumerated prior to cryopreservation. Numbers of CFU-GM were again calculated before reinfusion and the patients were divided into eight groups: 0.13-<0.4, 0.4-<0.7, 0.7-<1.0, 1.0-<3.5, 3.5-<5.0, 5.0-<10.0, 10.0-<20.0 and >20.0 (x 10(5)/kg). The minimum CFU-GM threshold (x 10(5)/kg) was found to be 1.0-<3.5 for platelets and 3.5-<5.0 for white blood cells. Higher infusion doses did not lead to significant benefits in hematopoietic reconstruction. These results indicate that preservation of a minimum of 7-10 x 10(5)/kg CFU-GM is recommended for the safe conduct of tandem HDCs.