[Epidemiology of chronic bronchitis]

In this short paper, the definition of chronic bronchitis, as it is now widely accepted by epidemiologists, is given and a comparison is made with the disease as usually referred to by general practitioners. Risk factors which are related to the development of the disease are then briefly discussed and the importance of internal parameters is underlined. At last, the methodological difficulties which arise in the assessment of the relationship between air pollution and respiratory symptoms are emphasized.