Aromatic DNA adduct levels were determined in macroscopically normal bronchial tissues from 98 patients undergoing pulmonary surgery. The mean DNA adduct level for the 45 current smokers was significantly higher than that of the 16 life-time non-smokers. There was a weak association between adduct levels and daily cigarette consumption above 10 cigarettes per day. DNA adduct levels in the 37 former smokers suggested an exponential form of adduct elimination with a rapid initial and a slower later phase after cessation of smoking. There was no quantitative association between bronchial DNA adduct levels and lung cancer.