The United States, in November, 1970, as part of the NATO/CCMS Air Pollution Pilot Study introduced the Low Pollution Power Systems Development (LPPSD) Program. This was in response to a recognized need for development of low pollution vehicles among the NATO allies. This report summarizes the presentations and discussions at the second LPPSD Symposium held on October 15-19, 1973, in Ann Arbor, Michigan. This symposium encompasses the regular AAPS contractors, coordination and progress meeting. Important elements of the technical presentations are presented. This includes: Gas turbines; Rankine power systems; Stirling cycle engines; Stratified charge engines; Diesel engines; Rotary engines; Electric cars; Alternate fuels; Hydrogen fuels; Schemes for reducing fuel consumption; and Reduction and measurement of lead particulates.