Charruyer and colleagues (this issue) report two significant advances to the field of cutaneous keratinocyte stem cells: a pair of new selectable markers that recognize a subset of α6(+)CD34(+) label-retaining cells, and an in vivo limiting dilution assay for keratinocyte stem cells with long-term repopulating ability. This work has important implications for keratinocyte stem cell identification and assay, as well as for the identification of target cells in non-melanoma skin cancer.