We have evaluated, over a mean follow up period of 3.7 (SD 1.8) years, the lung function in a group of 103 workers, according to the presence (36 workers) or absence (67 workers) of pleural plaques at chest Rx-films/HRCT. A Generalized Estimating Equation (GEE) approach was used to investigate the relation between the loss of pulmonary function and (i) presence/absence of pleural plaques, (ii) smoking status, and (iii) work seniority in work places with exposure to asbestos. The mean age, at the first examination, was 49 (SD 6) years and work seniority 25 (SD 7) years. Multivariate GEE approach to age- and height-adjusted spirometric data (236 measures of VC, FEV1 and 234 determinations of TLC), showed that pleural plaques were not associated with significant loss of pulmonary function. Smokers (> or = 15 py), when compared with no-smokers, showed significant loss of VC (-5.3%, p < 0.05), FEV1 (-8.4%, p < 0.001) and TLC (-4.0%, p < 0.05). An occupational history in work places with exposure to asbestos (ship building/repairing) was significantly associated with a slight, but significant (p < 0.05), 10-year decrease in VC (-3.1%) and FEV1 (-4.9%).