In accordance with various aspects of the invention, CXCR4 agonists,
including SDF-1 polypeptides and SDF-1 polypeptide homologues, may be
used in reducing the rate of hematopoietic cell multiplication. Methods
of the invention may comprise administration of an effective amount of an
CXCR4 agonist to cells selected from the group consisting of
hematopoietic stem cells and hematopoietic progenitor cells. Cells may be
treated in vitro or in vivo in a patient. A therapeutically effective
amount of the CXCR4 agonist may be administered to a patient in need of
such treatment. Patients in need of such treatments may include, for
example patients requiring bone marrow or peripheral blood stem cell
transplantation.