The associations between lung function measures (spirometry and peak expiratory flow lability) and estimated 20-yr ambient concentrations of respirable particles, suspended sulfates, sulfur dioxide, ozone, and indoor particles were studied in a sample of 1,391 nonsmokers followed since 1977. Differences in air pollutants across the population were associated with decrements of lung function. An increase of 54 d/yr when particles < 10 μ m in diameter (PM₁₀) exceeded 100 μ g/m³ was associated with a 7.2% decrement in FEV₁, as percent of predicted, in males whose parents had asthma, bronchitis, emphysema, or hay fever and with increased peak expiratory flow lability of 0.8% for all females and 0.6% for all males. An increase in mean SO₄ concentration of 1.6 μ g/m³ was associated with a 1.5% decrement in FEV₁, as percent of predicted, in all males. An increase of 23 ppb of ozone as an 8-h average was associated with a 6.3% decrement in FEV₁, as percent of predicted, in males whose parents had asthma, bronchitis, emphysema, or hay fever.