Substantial intimal changes, unrelated to aging, were found in resected lobes or lungs of 30 smokers with early obstructive lung disease (22 men, eight women: age range 46-74 years: forced expiratory volume in one second (FEV1)% predicted range 47-119%). Intimal area was measured using a digitiser and expressed as a proportion of the area enclosed by the internal elastic lamina (IEL), correcting for constriction (intima index). Arteries were subdivided into four size (length IEL) groups. For the smallest group (less than or equal to 600 micron length IEL) the mean intima index (II600) ranged from 0.09-0.34; half the values were greater than or equal to 0.20. Intimal abnormality was unrelated to the size or site of tumour or to macroscopic emphysema, and correlated weakly with pack years. II600 values were, however, significantly correlated with factors known to be affected by smoking such as alveolar wall surface area per unit lung volume, FEV1% predicted, and FEV1/FVC (forced vital capacity); these last two factors were also significantly associated with intimal abnormality in arteries measuring 601-1200 micron length IEL.