Viral vectors have been the favored delivery vehicle for gene therapy in recent years. Adeno-associated virus has become a candidate of great interest because of its biological properties which include site specific integration in human chromosome 19. The subject of this book is the use of adeno-associated virus as a new viral vector for gene therapy. AAV vectors can be used to deliver foreign DNA to mammalian cells with the goal of curing genetic diseases and allied conditions. The non-pathogenicity and site specific integration of AAV via a non-homologous recombination event into human chromosome 19 make this virus a very attractive vector. Data from in vitro and in vivo experiments are presented and discussed including recent studies with hematopoietic stem cells and non-dividing cells. Various protocols for preparing recombinant AAV vectors and their intracellular delivery are also extensively discussed. The first trial of AAV as vector for human gene therapy was conducted in late 1995.