For the first time, the book contains almost all available information about alien mammals in the ecosystems of Russia, scattered in numerous scientific publications, and also summarizes the authors' own materials on synanthropic and agrophilic species of rodents. The history and main ways of penetration of alien mammals into new habitats are described, their impact on natural ecosystems and local animal species is assessed, changes in their ranges and the current state of populations in newly settled territories are described.