Tobacco smoking and occupational exposure are the major factors responsible for chronic obstructive pulmonary disease (COPD) worldwide. The prevalence of this disease and its main risk factors were investigated in an area characterized by a high density of iron- and steelworking factories in North Italy. A total of 1,497 subjects (50% male) aged 40-59 yrs underwent an interview and a physical assessment, and 1,244 of them also underwent spirometry. The prevalences of COPD and asthma were 16.1 and 5.2% among males and 4.4 and 4.0% among females. COPD and respiratory symptoms were associated with both smoking and occupational exposure in males: the odds ratios for having been occupationally exposed among males were 2.3 (95% confidence interval 1.4-3.7) for COPD and 1.7 (1.2-2.6) for respiratory symptoms. No association was found between asthma and tobacco smoking or occupational exposure. The forced expiratory volume in one second and forced vital capacity were associated negatively with smoking and not associated with occupational exposure. In females, lesser effects of cigarette smoking on both self-reported respiratory diseases and lung function tests were found. The attributable risks of chronic obstructive pulmonary disease for smoking and occupational exposure among males were 52.9 and 8.8%, respectively, and 60.3% when considered together, whereas 18.8% of chronic obstructive pulmonary disease cases among females were attributable to smoking.