The development of recombinant DNA technology, and advances in understanding molecular biology, have made it possible to alter specific functions in cells by transferring foreign genes into them. Somatic cell gene therapy for inherited diseases attempts to insert a normal copy of the mutant gene into the diseased cells of a patient to permanently correct the defect. Gene therapy has entered clinical usage, and academic medical centers are beginning to develop the specialized interdisciplinary organizations and facilities that will be needed to bring gene therapy to the bedside. Yet, the human clinical trials now underway are highly experimental because current scientific understanding of the technology is in many ways inadequate. This review highlights some of the recent progress in gene therapy for inherited disorders in animal models and human clinical trials.