Background: Previous studies have shown associations between air pollution and risk for lung cancer. Ob jective: We investigated whether traffic and the concentration of nitrogen oxides (NOx) at the residence are associated with risk for lung cancer. Methods: We identified 592 lung cancer cases in the Danish Cancer Registry among 52,970 members of the Diet, Cancer and Health cohort and traced residential addresses from 1 January 1971 in the Central Population Registry. We calculated the NOx concentration at each address by dispersion models and calculated the time-weighted average concentration for all addresses for each person. We used Cox models to estimate incidence rate ratios (IRRs) after adjustment for smoking (status, duration, and intensity), environmental tobacco smoke, length of school attendance, occupation, and dietary intake of fruit. Results: For the highest compared with the lowest quartile of NOx concentration at the residence, we found an IRR for lung cancer of 1.30 [95% confidence interval (CI), 1.05-1.61], and the IRR for lung cancer in association with living within 50 m of a major road (> 10,000 vehicles/day) was 1.21 (95% CI, 0.95-1.55). The results showed tendencies of stronger associations among nonsmokers, among those with a relatively low fruit intake, and among those with a longer school attendance; only length of school attendance modified the effect significantly. Conclusions: This study supports that risk for lung cancer is associated with different markers of air pollution from traffic near the residence.