Stem cell trafficking between extravascular marrow sites and circulating blood is an essential part of the blood stem cell transplantation technology. Recombinant human G-CSF (rHuG-CSF) is widely used for stem cell peripheralization alone or together with chemopriming mobilizing early and pluripotent CD34+ cell subsets. New cytokine/chemokine mobilization regimens are under investigation such as combined rHuG-CSF and rHu thrombopoietin, rHuG-CSF and interleukin 3, rHuG-CSF and rHu stem cell factor, rHuG-CSF and Flt-3 ligand, human macrophage inflammatory protein, interleukin 1, and interleukin 8. Modifying the adherence of CD34+ cells to extracellular matrix molecules is a new mechanism by which hematopoietic progenitor cells are released into the circulating blood. Blocking the alpha4beta1 integrin receptor on CD34+ progenitor cells by using monoclonal antibodies specific for the heterodimeric complex alpha4beta1 has been shown to further increase the circulating stem cell concentration when given following rHuG-CSF priming. The current clinical research is primarily focused on improving stem cell mobilization efficiency in heavily pretreated and poorly mobilizing patients, and to decrease adverse effects of cytokine treatment.