This paper presents the results of several emission testing programs conducted by the U.S. Environmental Protection Agency. The test vehicles were primarily 1980 and 1981 passenger cars which were obtained at random from private owners. Some 1982 models were also tested. The 1328 vehicles were selected from the Los Angeles area as well as from a number of other low-altitude locations. The test sequence included the Federal Test Procedure, the Highway Fuel Economy Test and several short cycle tests. The primary purpose of the program was to gather information on current vehicles which could be used in calculations and projections of air quality and aid development of programs to improve it. The results of the program indicate that these vehicles are capable of maintaining low emission levels although high levels are also possible due to defects, deterioration, or tampering. Inspection/Maintenance programs are a feasible and effective means for correcting high levels when they occur.