Gene therapy is a therapeutic technique by which a functioning gene is inserted into the somatic cells of a patient to correct a genetic error or to provide a new function to the cell. Many different technologies are currently utilized to transfer new genetic information into animal cells. Although the gene transfer techniques used in experimental settings imply variable chemical, physical, mechanical and biological tools, only a few of them are practically useful for human gene therapy applications. Since 1989 we pioneered the use of retroviral vector-mediated gene transfer for gene therapy of human genetic diseases. Ongoing projects in the laboratory involve development of retroviral and lentiviral vectors for: 1) hematopoietic disorders, such as thalassemia; 2) muscular dystrophy; and 3) inherited skin diseases. Model systems include gene transfer into hematopoietic stem cells, muscle and epidermal progenitors, and the development of pre-clinical models for in vivo analysis of genetically-modified cells.