The purpose of the present study is to evaluate the possible association between bronchitis and exposure to man-made mineral fibres. The basis of the study has been cross-sectional data from the early 70's describing some 135,000 male Swedish construction workers. Data included information about exposure to asbestos and man-made mineral fibres, smoking habits and questions concerning symptoms of bronchitis. In non-smokers the rate-ratio of people exposed at least 3 years to non-exposed people is 2.68. In former smokers and in present smokers the corresponding values are 1.67 and 1.51 respectively.