This laboratory manual, published in cooperation with the International Society for Transgenic Technology (ISTT), provides almost all current methods that can be applied to the creation and analysis of genetically modified animals. The chapters have been contributed by leading scientists who are actively using the technology in their laboratories. Based on their first-hand experience the authors also provide helpful notes and troubleshooting sections. Topics range from standard techniques, such as pronuclear microinjection of DNA, to more sophisticated and modern methods, such as the derivation and establishment of embryonic stem (ES) cell lines, with defined inhibitors in cell culture medium. In addition, related topics with relevance to the field are addressed, including global web-based resources, legal issues, colony management, shipment of mice and embryos, and the three R: refinement, reduction and replacement.