Endothelial stem cells are thought to originate from hemangioblasts, the multipotent mesodermal derived cells which exist transiently during early embryonic development. They differentiate to form the cells of the endothelium (the inner lining of blood and lymphatic vessels), which include arterial, venous, capillary, and lymphatic endothelial cells. Mature endothelial cells perform essential functions such as controlling the flow of blood and lymph, regulating hemostasis, and trafficking leukocytes. Hemangioblasts are also the precursors to hematopoietic stem cells, which differentiate into the cells of the blood. While endothelial stem cells were historically considered to reside in the bone marrow, emerging evidence suggests they are instead found at the endothelial intima of existing blood vessels (the interface between the blood and the vessel wall). From here, they can be mobilized to enter the circulation and travel to sites of injury, where they serve to regenerate the endothelium. Numbers of circulating endothelial stem cells are used as indicators of an individual’s regenerative capacity, especially in relation to the cardiovascular system, and are known to decrease with age. As a result of their lineage, endothelial stem cells and hematopoietic stem cells have several markers in common. These include the cluster of differentiation antigens CD31 and CD34, the vascular endothelial growth factor receptors VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1), and the TEK receptor tyrosine kinase (Tie-2/CD202b). Markers that are more specific to endothelial stem cells include CD45, CD90, and CD117, as well as stem cell antigen-1 (Sca1), and vascular endothelial growth factor receptor 3 (VEGFR3). In recent years, other markers for endothelial stem cells have been proposed, including CD157, the endothelial protein C receptor (EPCR), interleukin-33 (IL-33), and SRY-box transcription factor 9 (Sox9). In addition, varying expression levels of CD31 and VEGFR2 have been suggested to help distinguish endovascular progenitors (CD31low VEGFR2−/low), transient cell types (CD31int VEGFR2−/low), and differentiated cells (CD31high VEGFR2high) cells. Endothelial stem cells have significant potential for therapeutic use, not least to repair damaged blood vessels and consequently reduce tissue inflammation and fibrosis. They are particularly of interest to researchers studying angiogenesis within the tumor microenvironment, where understanding how endothelial stem cells disrupt the basement membrane, migrate toward angiogenic stimuli such as VEGF, and subsequently proliferate to form new blood vessels may reveal novel ways to treat cancer. Notably, endothelial stem cell transplantation promises to promote angiogenesis in ischemic tissues (tissues with a restricted blood flow), including those seen in ischemic heart disease and critical limb ischemia. We offer a comprehensive range of endothelial stem cell markers including CD45 antibodies, c-Kit antibodies, IL-33 antibodies, and SOX9 antibodies. Our antibodies have been validated for use in multiple applications and a wide range of different host species, clonalities, and conjugates are available.