The invention relates to methods for manipulating hematopoietic progenitor cells and related products. In one aspect the invention relates to the use of agents that activate a PTH/PTHrP receptor to enhance the growth and maintenance of hematopoietic progenitor cells in vivo and in vitro, to enhance mobilization of hematopoietic stem cells, to improve the efficiency of targeting cells to the bone marrow, and/or to modulate hematopoietic progenitor cell function.