This book intends to be an introduction for those students who wish to become acquainted with the principles of plant virology. After a short history of the study of virus diseases the first part of the book is dedicated to methods of inoculation, the appearance of symptoms and their variable character, virus transmission and epidemiology including economic importance of virus diseases. In the second part methods of virus isolation and purification are described as well as methods in use for diagnostic purposes such as serology and electron microscopy. How to define the identity of a virus and the problems encountered in virus nomenclature are briefly though clearly discussed. The last part of the book deals with practical problems: how to control virus diseases by spraying, by hygienic measurements or hot water treatment, how to eliminate diseased plant material by laboratory tests or to improve the resistance by breeding. It is not surprising that this part of the book gives a good deal of information on potato virus diseases and on the Dutch organisations in charge of crop protection and disease control. A limited number of standard publications and general papers are mentioned at the end of each chapter. Finally a list of the most important handbooks is added.