All members of a large union were invited to participate in a study of potentially adverse effects of asbestos exposure. Clinical findings among 1,117 workers (90% of those eligible for examination) are presented in this study. Cough was much less common among those without a history of cigarette smoking, although duration from onset of employment did not appreciably affect the prevalence of cough among the smokers. Rhonchi present among nonsmokers were limited in extent, but were marked and diffuse among cigarette smokers. Although dyspnea was as prevalent among nonsmokers as in smokers forty years and more after onset of exposure, it was relatively uncommon and found only among smokers when examined shortly after onset of exposure. Cigarette smoking had less influence on the prevalence of rales among asbestos workers; both smokers and nonsmokers showed this finding when examined 30 years and more after onset of asbestos exposure. Analysis of powerhouse work experience and mask use as possible confounders indicated no difference in prevalence of these characteristics between the smokers and nonsmokers.