Obstructive changes in small airways have been described in patients exposed to asbestos and other mineral dusts. The physiologic significance of these small airways abnormalities and their relationship to dust burden and alveolitis remain unclear. We performed bronchoalveolar lavage (BAL) in 30 nonsmoking and 30 age-matched smoking subjects, all with mild asbestos and mixed dust exposure, to determine if parameters of lung dust burden correlated with spirometric evidence of airflow obstruction. Seventeen of 30 nonsmoking subjects and 24 of 30 smoking subjects met spirometric criteria for airflow obstruction. There were significantly more obstructed subjects in both dust exposed groups (P < 0.05) than in an age-matched nondust exposed group. There was, however, no significant difference in the number of obstructed subjects between the smoking and nonsmoking groups. There was no correlation in either group between airflow obstruction and total or differential cell counts, ferruginous bodies, total asbestos fibers, or the percent of free silica in the particulate fraction recovered by BAL. We conclude that evidence of small airways obstruction occurs commonly in occupationally dust exposed subjects and appears to be related to dust exposure per se and not to alveolar inflammation or fiber retention, important factors in the development of alveolitis and interstitial lung disease.