BACKGROUND Peripheral blood progenitor cells (PBPCs) are commonly collected and used to reconstitute hematopoiesis after high-dose chemotherapy. However, strategies for optimal collection and assessment of leukapheresis components are not standardized. METHODS Hematopoietic progenitor cell assays were performed on 369 leukapheresis components collected from 95 patients who had received doxorubicin-based chemotherapy and/or granulocyte-colony-stimulating factor (G-CSF). Precollection patient hematologic values, leukapheresis collection values, component hematopoietic progenitor cell assays, and patient outcome measures were summarized. The kinetics of mononuclear cell (MNC) and PBPC mobilization were assessed among four patient groups. RESULTS Patient group was a significant predictor of the peripheral blood MNC count on the day of collection (p<0.0001), and that value was a significant predictor of granulocyte-macrophage--colony-forming unit (CFU-GM) yield (p<0.0001). This relationship between the peripheral blood MNC count on the day of collection and CFU-GM yield differed according to patient group (p<0.0001). CFU-GM made up a larger fraction of peripheral blood MNCs collected from patients who received chemotherapy plus G-CSF than collected from those who received G-CSF alone. Moreover, the peripheral blood MNC count and the corresponding CFU-GM yield increased significantly on consecutive days of collection in patient groups receiving chemotherapy and G-CSF but were unchanged or decreased in patients receiving G-CSF alone. CONCLUSIONS The relationship between peripheral blood MNC count and leukapheresis component CFU-GM yield differed significantly between patients who received chemotherapy and G-CSF and those who received G-CSF alone for the mobilization of PBPCs. Patient peripheral blood MNC count and component CFU-GM yield are useful for both assessing and suggesting revisions to PBPC mobilization and collection strategies.