The present invention provides a method for enhancing the proliferation and/or hematopoietic differentiation and/or maintenance of mammalian stem cells. The method is useful for generating expanded populations of hematopoietic stem cells (HSCs) and thus mature blood cell lineages. This is desirable where a mammal has suffered a decrease in hematopoietic or mature blood cells as a consequence of disease, radiation or chemotherapy. The method of the present invention comprises increasing the intracellular level of a cdx in stem cells, including hematopoietic stem cells, in culture, either by providing an exogenous cdx protein to the cell, or by introduction into the cell of a genetic construct encoding a cdx. The cdx is selected from the cdx family and includes cdx1, cdx2, or cdx4. The cdx may be a wild type protein appropriate for the species from which the cells are derived, or a mutant form of the protein.