The textbook presents modern data on the systematics, morphology, physiology, and ecology of microorganisms, the distribution of useful and harmful species in nature; the causative agents of the most relevant animal diseases are described. The factors of pathogenicity of microorganisms, the mechanism of development (pathogenesis) of microbial infections, and the essence of antimicrobial protection are characterized. Methods of their laboratory diagnosis and means of specific prevention are described. Tests for self-monitoring of knowledge on the most important issues of veterinary microbiology are proposed.