This revised and updated edition of a much-acclaimed classic presents a collection of readily reproducible techniques for the generation and analysis of transgenic animals, with emphasis on the manipulation of the mammalian genome. It concentrates on the creation and maintenance of genetically modified murine strains, providing access to the germline by both conventional pronuclear injection, and by retroviral and adenoviral infection. Extensive coverage is also given to the generation, maintenance, and manipulation of embryonic stem cell lineages, with protocols for both constitutive and conditional (Cre-lox or the Flp-frt systems) gene targeting. Additional chapters provide cutting-edge techniques for the cryopreservation of both male and female germlines, for the generation of transgenic sheep by nuclear transfer, and for the basic analysis of transgenic organisms.