The importance of accumulating and documenting the knowledge relating to fish diseases need not be stressed when you consider the importance of traning people to recognize, treat and control diseases of fished. Adequately training people without textbooks is inefficient and expensice, and the fishing industries of the world would be poorly served were skilled fish pathologists not enthusiastic about sharing their knowledge and experiences. The purpose of this textbook is to provide modern, reliable information on fish diseases to teachers, researchers and students and to the increasing number of persons entering this new rapidly growing field of veterinary medicine.