Gene therapy is a novel concept of treating diseases at the molec­ ular level by rescuing genetic defects through the introduction of corrective genes. The knowledge of genetic defects underlying var­ ious diseases is being rapidly accumulated, and new genotypic findings are being reported with striking frequency. The elucida­ tion of the genetic background of many diseases, including hered­ itary blistering and hyperkeratotic skin disorders, has provided the necessary knowledge to correct inborn genetic aberrations in ani­ mal models and patient-derived tissue. However,skin is not only a target organ for gene therapy ofcutaneous disorders. Dueto its bio­ logical properties, easy accessibility, and convenient, established culture conditions and grafting techniques, skin has rapidly be­ come an important target for correcting other diseases as well. Both skin fibroblasts and epidermal keratinocytes have been successfully transfected ex vivo and in vivo using viral and nonvir­ al gene transfer methods. Notably,in the first corrective gene ther­ apy approach in 1987, fibroblasts from adenosine-deaminase (ADA)-deficienthumans with severe combined immunodeficiency (SCID) syndrome were transduced using retroviral vectors. More­ over, skin cells are capable of synthesizing various proteins that are therapeutic, either locally or systemically. Human epidermal grafts expressing human growth hormone after retroviral gene transfer and grafting onto athymic mice released human growth hormone into the bloodstream of the transplanted mice, for a lim­ ited time.