Current therapies for most human genetic diseases are inadequate. In response to the need for effective treatments, modern molecular genetics is providing tools for an unprecedented new approach to the treatment of diseases; e.g. the direct manipulation of mutant genes or the input on new therapeutic genes. The treatment of human disease by gene transfer has now moved from the theoretical to the practical realm. With the initiation of clinical trials involving somatic gene therapy in different countries, a critical assessment of the different aspects involved with this new technique is necessary. This volume provides an overview on all these interdisciplinary aspects by some well known experts all over the world.