Atmospheric carbon dioxide was investigated as an indicator of air quality in urban atmospheres comparing hourly, daily, and seasonal variations in carbon dioxide with carbon monoxide, nitric oxide, nitrogen oxide and oxidant. Because the complex meteorological-photochemical phenomena involved in West Coast basins causes the chemical constituents to change in concentration during the day, statistical correlations on an hour by hour or a minute-by-minute basis were found to be meaningless. Seasonal, daily, and hourly relationships are graphically presented and discussed. Results from the use of a mobile carbon dioxide sampler used on the freeway to evaluate the line source of air pollution are presented. The results of a study of atmospheric carbon dioxide over the ocean shows clouds of air containing significantly high amounts as far as 800 miles off shore that are traceable to the Los Angeles metropolitan area. Indications are that carbon dioxide concentrations may be used as an index of air pollution, and could be used to tell much about the general meteorological phenomena of a basin.