The textbook discusses the theory of internal combustion engines, kinematics, dynamics, engine balancing, their design features, power supply, pressurization, cooling, lubrication, start-up systems. Special chapters are devoted to environmental indicators, engine load modes when working on construction and road machines, methods for selecting engines. The focus is on diesels. The 2nd edition (1st edition in 1978) reflects the latest achievements in the science and practice of engine building and operation of engines, supplemented with information on thermal loads, thermal intensity, toxicity and acoustic indicators of diesel engines.