The effect of air pollution on lung function in children and youths ages 6-24 years was examined, after controlling for age, height, race, sex, body mass, cigarette smoking, and respiratory symptoms. Forced vital capacity (FVC), forced expiratory volume at 1 sec (FEV1), and peak expiratory flow all showed statistically significant (P less than 0.05) negative correlations with annual concentrations of total suspended particulates (TSP), nitrogen dioxide, and ozone. The ozone and NO2 relationships were highly significant. The TSP relationship was less significant. No relationship was found with sulfur dioxide. The relationships held whether or not children with respiratory conditions, or smokers were included. Demographic and geographic variables had little or no impact on the pollution relationships, which also held when only persons still residing in their state of birth were considered. Essentially identical relationships were found using pollution averaged over 2 years. The relationships held across most NO2 concentrations, but were only apparent at high particulate and ozone concentrations.