In this textbook a systematic, concise and up-to-date account of the main sections of microbiology, virology, and immunology is given. The description of separate causative agents is presented in a certain sequence. First of all, the morphology and structure of microbes are given, followed by data on cultivation, enzymatic properties, antigen structure, classification, etc. Taxonomy and nomenclature of microorganisms are given in accordance with the International Nomenclature accepted in Soviet periodical and monographic literature. The morphology of microbes is described using the latest data on the structure of microbial cells obtained with the aid of light and electron microscopy and phase-contrast and luminescent microscopy of ultrathin sections. The textbook contains new data on the morphology of viruses, on the microflora of the external environment. A section on fungi is systematized. The textbook is intended for students of medical institutes. Kirill Pyatkin, Doctor of Medical Sciences, Professor, is Head of the Department of Microbiology at the Crimea State Medical Institute in Simferopol. He is the author of 78 published papers, 6 of which are monographs. His main works are dedicated to the problems of pathogenesis and immunity of diphtheria and are well known to scientists beyond the limits of the USSR. He has good experience as a teacher in higher institutions. He has published Lectures on General and Special Microbiology, Handbook of Practical Work in Medical Microbiology, and other works for students of medical institutes. In the Soviet Union his textbook has been reprinted twice. It has also been published in Spanish.