The first unequivocal success for Gene Therapy was reported in April 2000 for X-SCID patients. Pioneering stem cell/gene therapy clinical trials are the focus of this book. Therapy successes such as the X-SCID trial and improved ADA-SCID ones are presented together with pioneering angio/vasculogenic clinical trials mediated either by transient gene therapy or emerging autologous stem cell transplantation. Highlights also include 1) promises of the breakthrough combination of stem cell- and transient gene-therapy, 2) gene therapy trials for neurodegenerative disease on non-human primates where long-term gene therapy might involve brain stem cells, and 3) the first clinical trial with non-invasive monitoring of therapeutic gene expression as a prospective conclusion.