Human embryonic stem cells (hESCs) have been traditionally characterised using a panel of antibodies to cell surface markers, such as SSEA-3, TRA-1-60 and TRA-1-81; however, none of these traditional markers are entirely specific to hESC cells (Laslett et al., 2003). The novel TG30 antibody, which has been shown to be a reliable cell surface marker for the detection and characterization of pluripotent human embryonic stem cells (Adewumi et al., 2007), recognizes a cell surface epitope of a tetraspannin protein that has been further identified as CD9. When this antibody is used in conjunction with the TG343 antibody, TG30 has been successfully shown through flow cytometric assays to be a robust and rapid tool for the purification and selection of live Oct-4-positive human embryonic stem cells from a mixed population of differentiated cell types.