In this book the viruses are treated as members of an order consisting of 13 families, 32 genera and 248 species. Bacteriophages constitute one subgroup, viruses causing diseases in seed plants are a second subgroup, and the third subgroup consists of viruses causing diseases in animals. The author points out that this subgrouping of viruses may have to be changed with advances in knowledge. Each species is discussed first from the standpoint of derivation of the name and is followed, where applicable, by the headings: common names, host, insusceptible species, geographic distribution, induced disease, transmission, serologic relationships, immunologic relationships, thermal inactivation, filterability, other properties and literature. The large number of viruses now recognized makes it imperative that they be named and classified. Some time will probably pass, however, before the average physician recognizes Legio debilitans as poliomyelitis virus and Erro scelestus as St. Louis encephalitis virus. The book is well