As we move into the twenty-first century the spread of affluence to a greater portion of an ever growing world population, coupled with dwindling reserves of crude oil, will make it imperative that we simultaneously protect our environment and enhance the fuel efficiency of transportation vehicles. Although reduced vehicle weight is the major contributor to conservation, it is argued that safety considerations limit vehicle size reduction. The engine thus remains an important component in meeting the needs of the new century; it is the primary subject of this lecture. The lecture first specifies those areas of engine design which provide the best opportunities for changes that will meet the needs of fuel economy and reduced emissions at an affordable cost. The discussion then concentrates on defining the pathways to achieving such goals. In particular, the tools available to perform the needed studies are discussed. The lecture ends with a discussion of the types of programs and methods of technical interchange required to produce a new generation of engines. [S0742-4795(00)00202-7]