Hematopoietic stem cell transplantation has been extensively exploited as a therapeutic and research modality and has revolutionized current patient care. At present, more and more medical centers use peripheral blood progenitor cells for transplantation by mobilizing hematopoietic stem cells from bone marrow to peripheral blood because of potential advantages of peripheral blood stem cell transplantation over bone-marrow transplantation. Different effective mobilization regimens have been developed recently with chemotherapeutic agents, hematopoietic growth factors or their combination. This article reviews current developments related to hematopoietic stem cell mobilization including the biology of hematopoietic stem cells, strategies for mobilization, management for mobilization failure, mechanisms of mobilization, and side effects during mobilization. Finally, the Initiation-Amplification-Emigration-Adaptation Model is proposed to help aid understanding of the mechanisms of hematopoietic stem cell mobilization and to stimulate development of novel and optimal mobilization strategies for patient care.