Plerixafor is an inhibitor of CXCR-4 (CXC chemokine receptor-4)/SDF (stromal cell-derived factor)-1 binding used in combination with granulocyte colony-stimulating factor (G-CSF) for mobilization of autologous peripheral blood hematopoietic stem cells (HSCs). We developed a data-generated, cost-saving decision-making algorithm that uses the CD34+ count in the peripheral blood on the fourth day of G-CSF administration (PB-CD34+), and the collection target (T-CD34+) to decide between continuing G-CSF only (G approach) or adding plerixafor to the mobilization regimen (G+P approach) aiming at the lowest cost. The G+P approach was more cost-effective with lower PB-CD34+. It was possible to determine, for each T-CD34+, the maximum PB-CD34+ for which the G+P approach is cost-effective, generating an algorithm for the use of plerixafor. We validated this algorithm in a cohort of 34 patients undergoing HSC mobilization. In all, 11 patients completed collection on the G approach and 23 patients on the G+P approach, with 91% of the patients completing collection within the predicted number of apheresis sessions. All patients who underwent transplantation engrafted with minimal differences in engraftment time between G and G+P approaches. This validated algorithm provides a potential cost-saving decision tool for the use of plerixafor in autologous HSC mobilization. © 2011 Macmillan Publishers Limited All rights reserved.