The Two-Stroke engine revival is seen as a way to reduce the size and weight of engines. IFP has been one of the first engine research centres involved since the early eighties in this promising way of a new generation of highly efficient engines. Since this date, a large number of car manufacturers and research laboratories around the world have engaged research and development efforts in this new field. In these conditions, it was essential for IFP to examine the different research works, technological choices, and new ideas. The systematic study of the patents published since 1981 and their statistical analysis represent an interesting tool to follow the main trends of the research in this domain. More than 4200 patents were selected as relevant for this study. The results of this patent analysis allow firstly, to distinguish the time of emergence of new research and development, and secondly, to give ideas about their respective potential in terms of R & D, about the technical difficulties they encountered and finally, about their strategy in this field and their policy in terms of industrial property. This competitive intelligence based on patents analysis has been proved efficient and useful from several points of view. The analysis of all innovations generates new ideas for researchers; it also allows the guidance of research work in the ways which will answer to the future needs of the market while avoiding solutions locked by competitors. Finally, it is an help in the definition of a policy in terms of industrial property.