Many groups of students and research workers need to acquire a working knowledge of mammalian anatomy and histology. Such knowledge can be acquired from books though this a very poor second best to acquiring the information from the animal itself. Dissection and the preparation and examination of histological sections remain the best methods. Knowledge of anatomy is necessary for all those who use histological techniques: the taking of specimens for histological work presumes some knowledge of anatomy. But not all those who work with small mammals receive training in mammalian anatomy and histology. In the past this was less of a problem: zoology was grounded in comparative anatomy and morphology; dissection formed a part of every school, college and undergraduate course in biology and zoology. This is less the case today. In addition, not all those who work with small mammals, for example, in toxicology laboratories, have a zoological background. In this book we have tried to provide an introduction to the anatomy and histology of one small mammal, the rat. The rat, and its relative the mouse, are the most widely used experimental animals and many research workers and trainees need to be familiar with these species. We have assumed that the reader wishes to learn by practical experience: our approach is based on dissection and on the preparation of histological sections. Our earlier book, ‘Histological Techniques: An introduction for beginners in toxicology’ deals with techniques in some detail. In our descriptions of dissections we have stressed both anatomical points and the techniques applied in postmortem examination of experimental animals.