Mesenchymal stem cells (MSCs) are multipotent, self-renewing cells with the ability to differentiate into a variety of cell types, including osteoblasts, chondrocytes, myocytes, and adipocytes. Unlike embryonic stem cells, they can be derived from postnatal tissues, such as the umbilical cord, cord blood, amniotic fluid, bone marrow, and adipose tissue. To identify human MSCs, a number of stem cell markers are commonly used. Stro-1, an endothelial antigen, may perhaps be the most well-known marker. Others include surface proteins such as Endoglin (CD105), VCAM1 (CD106), CD73, CD90, CD44, CD13, CD29, CD146, CD166, and Sca-1. CD45 and CD19 are reported negative markers. Antibodies that target these markers may serve as useful tools in investigating mesenchymal stem cells.