Book excerpt: Thirty protocols by leading researchers describe in detail all the essential molecular methods for working with gene transfer systems, along with the methods for gene transfer to specific tissue types either in vivo or ex vivo. The easily reproducible methods range from those for specific viral and nonviral for both genetic and acquired diseases, to those concerned with gene delivery to particular tissues. Methods for applying specific therapeutic systems, such as ribozymes and tumor supressor genes for the treatment of AIDS and cancer, are also included in this authoritative collection.