Three cross-sectional studies were conducted in an effort to investigate the effect of automobile exhaust on respiratory symptoms. Female adult subjects were selected from residents who lived near roadways that were subjected to very heavy traffic. A standard questionnaire was administered to approximately 5,000 people. Distances of the residences from the roadside were adopted as an index of exposure to automobile exhaust. The estimated odds ratios for chronic cough, chronic phlegm, chronic wheeze, shortness of breath, and chest cold with phlegm, relative to distance from the roadside--adjusted by age, smoking status, years at residence, occupation, and type of home heating-ranged from 0.76 to 2.75. The 95% confidence limits of the odds ratios for chronic cough and chronic phlegm excluded or approached 1.00 in each of the studies. This suggests that exposure to automobile exhaust may be associated with an increased risk of certain respiratory symptoms.