Gene transfer has become a reality during the last decade. The basic principles of molecular biology, gene transfer, and the problems associated with this new technology have direct implications for the treatment of pediatric surgical patients. Research into applications of gene transfer in the treatment of disorders of the bone marrow, cancer, hemophilia, hepatic and metabolic disease, cystic fibrosis, and vascular disease is rapidly progressing. These areas of research may dramatically affect the care of pediatric surgical patients in the future.