In view of the growing interest in the study of mites associated with rodents and the urgent need for identification tools, the Zoological Institute of the Academy of Sciences of the USSR undertook the preparation of this identification guide (Fauna of Small Animals, Issue 28). This publication represents the first attempt to compile identification keys for all groups of mites found on rodents and in their nests; therefore, it cannot claim to be exhaustive. The degree of study of various mite groups within the USSR is highly uneven. For example, chigger mites and certain other groups can be identified to species level, whereas representatives of poorly studied groups, particularly non-parasitic forms (such as Oribatei, Tarsonemini, and some Gamasoidea), can often be identified only to genus or even merely to family. This guide includes 63 families, 75 genera, and 249 species (including subspecies). The contributors to this identification guide include staff members of the Zoological Institute of the Academy of Sciences of the USSR (N. G. Bregatova, V. B. Dubinin, E. N. Pavlovsky, and G. V. Serdyukova); the Department of Entomology of Moscow State University (E. M. Branova-Zakhvatkina, A. A. Zakhvatkin, and A. B. Lange); the Department of Parasitology and Medical Zoology of the Gamaleya Institute of Epidemiology and Microbiology of the Academy of Medical Sciences of the USSR (A. A. Zemskaya and E. G. Shluger); and the Leningrad Institute of Applied Zoology and Plant Protection (V. I. Volgin). E. N. Pavlovsky wrote the preface, the introductory essay on the significance of mites and the current state of their study (including a list of mites recorded from rodents and their nests), and the section on the family Ixodidae; he also served as the general editor of the guide. A. A. Zakhvatkin prepared the general review of mite morphology and development, as well as the identification keys for mite superfamilies and certain families found on rodents. Together with V. I. Volgin, he also wrote the section on storage mites (Acaridae). E. M. Branova-Zakhvatkina authored the section on oribatid mites. V. B. Dubinin contributed the chapters on itch mites, hair mites, and gland mites, as well as the general account of mites of the family Myobiidae. V. I. Volgin prepared the section on the predatory mite family Cheyletidae and the identification keys for Myobiidae. E. G. Shluger wrote the chapter on chigger mites and supplied original illustrations. A. B. Lange prepared the overview of gamasid mites and the identification keys for the genera Laelaps and Oryctolaelaps; he also produced original microscope plate illustrations for these sections. A. A. Zemskaya prepared and illustrated the taxonomic section on the family Dermanyssidae. N. G. Bregatova was responsible for the remaining gamasid mite sections, including the family-level keys; descriptions of the families Rhodacaridae, Parasitidae, Veigaiidae, Ascaiidae, Macrochelidae, and Pachylaelaptidae; and the identification keys for the family Haemogamasidae and certain members of Laelaptidae. She also wrote the chapter on methods of collecting mites. G. V. Serdyukova contributed the section on chigger mites. Some of the illustrations in the book are original, while others have been reproduced from the works of Soviet and foreign acarologists. The Zoological Institute hopes that this volume will promote the active collection of materials on the mite fauna of our country and stimulate more detailed research on insufficiently studied groups. In addition, this identification guide is essential for experimental work in epidemiology, veterinary epidemiology, and agriculture, as well as for the development of measures for mite control. The Zoological Institute will be grateful for any comments or suggestions concerning the guide. Correspondence should be sent to: Zoological Institute, Academy of Sciences of the USSR, Universitetskaya Embankment 1, Leningrad 164. Work on the identification guide to rodent mites will continue as new materials on the mite fauna of the USSR become available. The Institute would be grateful to receive collections of mites from rodents; parcels should be sent to the same address. Reprints of publications on mite research, or information about newly published works, are also welcome for inclusion in the Institute's library holdings. Director of the Zoological Institute of the Academy of Sciences of the USSR Academician E. N. Pavlovsky