Rapid developments continue to take place in the research of viruses, the causative agents of infectious diseases in humans, animals, plants, invertebrates, protozoa, fungi, and bacteria. A still growing number of more than 30,000 viruses, virus strains, and subtypes are being tracked in various specialty laboratories and culture collections. In this situation of expansion and specialization, the International Committee on Taxonomy of Viruses was founded to establish, refine and maintain a universal virus taxonomy system giving information to virologists about the characteristics of the different groups of viruses. The Committee's Sixth Report includes one order, 71 families, 11 subfamilies, and 175 genera and more than 4,000 member viruses. On 600 printed pages large amounts of molecular biologic data, illustrated by micrographs and virion diagrams, gene maps and tables give a comprehensive overview and prove helpful in teaching, in diagnostics, in scholarly research, and in the practical areas of medicine, veterinary medicine, plant pathology, insect pest management, and biotechnology.