The objective of this investigation is to determine the role of childhood respiratory illnesses, familial factors and cigarette smoking, operating independently or interacting with each other, as predictive risk factors for the development of chronic bronchitis (CB) and obstructive airways disease (OAD). A cohort of children age 5-9 years and their families has been established and will have been followed for 2 years (NHLI contract NO1-HR3-2906). Detailed information is or will be available concerning respiratory illness history, cigarette history, pulmonary function and air quality for the cohort and its environment. Families will have been stratified as to their risk of developing CB and OAD. The present protocol proposes to prospectively study this cohort on an annual basis for 5 years. Home visits will be made. Data will be collected using standardized questionnaires and a portable spirometer which has undergone extensive field testing. The study seeks to: 1) Determine the value of the hypothesized risk predictors to actually predict the occurrence of chronic respiratory symptoms and or the occurrence of large deviations from expected levels of pulmonary function in the index children. 2) Evaluate the contribution of familial factors to the risk of developing CB/OAD. 3) Study the determinants of the individual susceptibility to the functional and symptomatic consequence of tobacco use.