This longitudinal study was initiated in 1975 when a stratified random sample of children, ages 5-9 years and living in the East Boston area of the City of Boston, was selected. Annual lung function tests were performed on the children and their families and questionnaires administered on respiratory illness history, smoking history, disability from cardiac disease, age of menarche in female children and demographic data such as type of heating, type of fuel for cooking, types of air purifying devices, and area of residence. A subset of the cohort had repeated measures of eucapneic hyperventilation with cold air. The cohort was also studied with helium-oxygen protocol. Analysis focused on validation of existing models, including the autoregressive model, for lung growth in children and adolescents and the decline in growth in adults.