At present there is no methodology available for assessing lung function and growth in young children that is painless, non-threatening, fast and at the same time is sensitive to early abnormalities in airways function or ventilization inhomogeneity. Thus at present our knowledge of patterns of lung growth and functions as they relate to age, sex, size, and lung disease is scanty. Similarly, we do not have the methods or basic information required to assess risk factors in young children for the possible development of chronic lung disease such as passive smoking or viral respiratory tract infections. One of the priorities of the 1983 NIH Workshop On Passive Smoking was the development of such methods. The objectives of this proposal are: 1) to develop a methodology appropriate for assessing lung growth and function in young children; (2) to determine the precision, specifically, and variability of the method and to develop reference standards for young children; (3) to test the hypothesis that the method to be used has the sensitivity required to separate out "healthy" from "non-healthy;" (4) to test the hypothesis that lung growth is diffferent in boys and girls; (5) to test the hypothesis that ventilation homogeneity changes with age; and (6) to use the methodoligy which is developed in a long-term collaboarative study of the natural history of alpha1 antitrypsin defidiency. The method to be used is on-line computerized moment analysis of multibreath nitrogen washout (MBNW). The technique requires only that the subject quietly breathe oxygen for less than 2 minutes, and the analysis of the curve is independent of body size, lung size, tidal volume, or respiratory rate. The data obtained from the curve include functional residual capacity, moments 0, 1 and 2 of the MBNW curve, moment ratios, lung clearance index, and other indices of the washout. The required software has been developed and preliminary data has been obtained from 36 healthy children ages 2-6 years, 10 children with cystic fibrosis of the same age, and 5 young healthy adults. The data to date indicate that moment analysis of MBNW curves has the ability to fulfill the objectives of the proposal. The long-range plans are to use the information obtained from this study in long-term studies of risk factors for the development of chronic lung disease. The beginnings of one such study, a long-term collaborative description of the natural history of alpha1 antitrypsin deficiency, is included as part of the grant proposal.