Abstract: Gene transfer of genetic material with viral vectors or plasmid, in combination with a wound treatment chamber, into keratinocytes, especially those including a high percentage of epidermal stem cells, has been demonstrated to be particularly effective as a means of implanting genetically engineered cells and obtaining long term survival. By employing the wound chamber system, direct in vivo gene transfer can also be done to exposed cells in an open wound. Skin stem cells which are located in the hair follicles are used to greatly enhance long term survival. The use of the wound chamber system for gene transfer also allows non-invasive assessment of the success of transfer by assaying for the presence of the expressed protein in wound fluid, in contrast to the prior art use of invasive techniques, such as biopsies, in order to achieve the same assessment of early expression.