Improved methods and pharmaceutical compositions are provided herein for mobilizing hematopoietic progenitor cells from bone marrow into peripheral blood, comprising the administration of an effective amount of an inhibitor of GTPases, such as Rac1 and Rac2 alone or in combination. Specifically, methods are disclosed for mobilizing hematopoietic stem cells into a subject's peripheral blood. In particular, embodiments of the method involve inhibition of both Rac1 and Rac2 GTPases to increase the numbers of hematopoietic stem cells into a subject's peripheral blood of a subject. The subject's blood can be processed and used to repopulate the destroyed lymphohematopoietic system of a recipient and may in the future be utilized to repair a variety of non-hematopoietic tissues. Therefore, hematopoietic stem cells mobilized into a subject's peripheral blood by the method of the invention is useful as a source of donor cells in bone marrow transplantation for the treatment of a variety of disorders, including cancer, anemia, autoimmunity and immunodeficiency. They can also be used for increasing white blood cell survival and for chemotherapy.