This paper presents results of a program conducted during 1968 to evaluate the capability of an engine tune-up inspection to reduce exhaust emission levels of a car population. Tune-up parameters such as ignition timing and carburetor idle mixture and speed were evaluated. The test sample included 478 privately-owned passenger cars, 1959 through 1968 models, being operated in the Los Angeles area.As received average exhaust emission levels in this population were found to be 675 ppm HC and 2.73% CO. Adjustment of only idle speed and mixture reduced HC by 10 percent and CO by 16 percent, while oxides of nitrogen increases slightly. If applied to the car and light truck population of Los Angeles County, this tune-up program could result in reducing the daily output of hydrocarbon by 100 tons and carbon monoxide by 1050 tons. This in effect would advance the present automotive exhaust emission control program in California by 2 to 5 years.Considering the small annual cost per car, less than $3, the effectiveness in reducing exhaust emissions to the atmosphere, and the high customer acceptance of the adjustments at 93 percent, this type annual minor tune-up approach is ideal for current statewide programs of emission control from the automobile.