This book is about transgenic animals - animals into which new genes have been artificially introduced. It has chapters by leading authorities on the present state of play regarding the application of the transgenic technology to different animal groups. A great range of animal types, ranging from protozoan cells, through nematode worms and fruit flies to many higher vertebrates, have been used in this experimental way and this book provides an in-depth, up-to-date, comprehensive and authoritative account of the work with all such animal types. The likely impact of transgenic animals on the future development of agriculture and medicine is very great; at the same time they provide an unrivalled experimental system for the study of gene regulation, genetic aspects of disease, and gene therapy. One of the objectives of the book is therefore to set transgenic animals in the context of their present and future contributions to medicine and agriculture.