The epidermis is readily accessible for genetic manipulation and is easily monitored. Using pig skin because it is very similar to human skin morphologically, we have developed a method to transiently express biologically active factors in epidermis. Following direct injection of naked plasmid DNA into skin, DNA is taken up and transiently expressed at high levels by epidermal keratinocytes. Injection of interleukin-8 plasmid DNA into skin results in the appropriate biological response of neutrophil recruitment, demonstrating functional utility. In addition to this model's therapeutic uses, the biological effects of structural gene products on the epidermis could also be studied in vivo.