Cigarette smoking is recognized as the most important factor in the development of chronic airflow obstruction, yet only a minority of cigarette smokers develop clinical disease. In 1985, interest focused on the role of increased levels of airways responsiveness and atopy as possible potentiating factors for the development of chronic airflow obstruction. Then current epidemiologic studies had data on only one of these potential risk factors or were too small to adequately address the issues involved. The present study assesses both airways responsiveness and atopy.