The state of Washington instituted an automobile emissions testing and maintenance program in the Seattle-Bellevue area in 1982, the purpose of which is to reduce carbon monoxide levels to meet the federal standards. This study measures the impact of the program at two air quality monitoring stations in Seattle, comparing these stations to one in Tacoma. Six separate analyses of the program's effect on carbon monoxide are presented that differ by location, time period, and statistical method used. None of the six shows a significant program impact. The conclusion is that the possibility of a significant decline in carbon monoxide due to the testing program is remote.