Among the subsets that define hematopoietic stem cells (HSCs), CD34(-) c-kit(+) Sca-1(+) lineage marker(-) (CD34(-)KSL) cells are regarded as one of the populations that have the highest enrichment of HSCs in adult mouse bone marrow. Here, we demonstrate that long-term repopulating hematopoietic stem cells (LTR-HSCs) have high expression of CD61 (integrin beta(3)) within the CD34-KSL population. Approximately 60% of CD34(-)KSL cells showed high expression of CD61. CD61(High) CD34(-)KSL populations also exhibited significantly greater properties of HSC, such as expression of HSC markers, the side population (SP) phenotype, and ability for long-term repopulation. In both SP cells and non-SP (NSP) cells, CD61(High)CD34-KSL cells also contained significantly more LTR-HSCs than CD61(Low/-)CD34(-)KSL cells. Our results indicate that CD61 is exploitable for HSC enrichment as a supportive positive cell surface marker. (c) 2007 Elsevier Inc. All rights reserved.