Protocols for the purification of CD34-KSL cells, CD34+KSL cells, SP cells, and Tip-SP CD34-KSL cells are described. Mouse hematopoietic stem cells are highly enriched in the CD34-KSL and SP fractions. These two populations overlap one another. A nearly homogenous population of HSCs can be obtained by isolating Tip-SP CD34-KSL cells. One of the earliest progenitor cell populations is CD34+KSL cells.