The prevalence of chronic respiratory illness among 3,500 parents of high school students was studied in Chattanooga during the last quarter of 1970. Data were obtained from parents of students in four senior high schools, the neighborhoods of which had an exposure gradient to atmospheric nitrogen dioxide. The smoking habits of respondents were measured by the usual questionnaire techniques and by carbon monoxide concentrations in alveolar breath samples. Lung function was measured by one second forced expiratory volume (FEV) tests. Breath carbon monoxide levels were correlated with smoking habits, FEV and severity rating of chronic respiratory illness. FEV test results, corrected for height, age, sex, race, and CO, were singificantly lower among sample parents living in the high-nitrogen dioxide exposure area. Residents of that area did not show a significantly higher prevalence of chronic respiratory illness.