This book analyses the technology of spark ignition two-stroke engines. The presentation is simple and comprehensive. The description of the operating cycle, the fluid dynamics, the lubrication and the cooling systems is followed by painstaking analysis of the mechanical organs, with the materials and the manufacturing processes employed to produce them. The book is completed by an overview of the history and evolution of these engines and by an examination of the principal types and the diverse fields in which they are employed. A section of the work is dedicated to an in-depth analysis of the ignition and combustion phases and the formation of the air-fuel mixture, with particular attention paid to the most recent injection systems.