If you want practical information on how to use this book please refer to Note to the Readers p. VII. Histochemistry and cytochemistry are essential tools in biomedical research and routine service laboratories. Most texts on histochemistry fall into one of two categories: 1. Encyclopaedic texts covering all or nearly all information available on the whole or selected parts of histochemistry. 2. Reviews or surveys of methods found to be useful by the author(s). While the former category often appeals to the more philosophically inclined reader, direct guidance on the selection of technique may be difficult to find. In contrast, the latter category are often excellent sources for details on how to perform a particular method with a reasonable chance of success. Consideration of the exact mechanism of staining, of possible reasons for failure, and of alternative techniques are, however, frequently lacking. This book is an introduction to the scientific basis of histochemistry and is intended to provide a background for the selection and development of appro priate methods. It is not a cook book and readers expecting exhaustive methodological descriptions will be disappointed. Although most ofthe contributors to this book would not describe themselves as histochemists, they have all at some time found it essential to develop a basic understanding of histochemistry. This book contains the information they would have greatly appreciated ready access to at that time.