The paper reports the results of a prevalence study on functional impairment and chronic bronchitis in 733 foundry workers and in a control group of 1041 workers not exposed to the specific risks of the iron and steel industry. This study is the first part of a longitudinal study lasting 5 years within the framework of the Fourth Research Programme of the European Coal and Steel Community. Data on microclimate and particulate pollution for the various departments showed uniformly cold and damp conditions. Concentrations of pollutants were generally below the current T.L.V.'s. The subjects were subdivided into groups according to age, smoking and length of exposure. All the subjects were administered the "E.C.S.C. Questionnaire for the study of chronic bronchitis and pulmonary emphysema" and underwent a chest X-ray and spirometry to measure FVC, FEV1 and Vmax 50. The prevalence of functional impairment and chronic bronchitis was higher in the foundry workers than in the group of non-exposed workers. A statistical standardization was made of the effect of age and smoking thus accentuating the effect of exposure. The results are compared with the data obtained by other epidemiologic studies on working populations exposed to a similar risk.