Abstract
The concept of human gene therapy arose in the early 1970s and has now been the subject of many clinical trials in human patients. To date, there have been no truly convincing therapeutic successes, but any disappointment with that fact is due more to the exaggerated levels of our expectations than to any failure of concept. The concept of human gene therapy has been a startling success and it is now one of the most important driving forces in medicine. Current tools have simply not been adequate for the difficult job of efficient and stable gene delivery, faithful and regulated gene expression and clinical correction of a human disease. Nevertheless, progress toward human gene therapy is rapid and inexorable and the second phase of human gene therapy, the implementation phase, will soon also succeed.