The book appeared in two previous Slovak editions for university students in Czechoslovakia. This edition presents a completely new version updated according to recent advances not only in immunochemistry and essential immunology but also in molecular biology, biochemistry and molecular genetics. The scope of the book is considerable since the goal was to cover the field of immunochemistry from the widest point of view including both the topic and methods of contemporary immunochemistry. Each chapter provides basic information on a specific subtopic, clearly and understandab ly, and presents principles of individual immunochemical methods. I am confident that the book will fill the gap between the books on essential immunology and highly specialised books on individual areas of immunoche mistry (e. g. on antibodies, antigens, numerous immunochemical techniques, etc. ). It may also prove useful for beginning investigators from different biological and medical fields as it supplies basic information needed for solving their scientific problems by immunochemical approaches. I do hope that readers will find the text stimulatory and pleasury to read. I wish to thank all colleagues and friends for supplying their own results, suggestions and for their encouraging comments. My thanks go also to the editors and publishers for their valuable contribution to the preparation of the book. 1 Introduction The term immunochemistry was coined by the Swedish chemist ARRHENIUS who used it for the first time in his lectures in 1907.