Most of the authors are members of the Occupation and Epidemiology Assembly of the ERS. The Assembly is active in developing epidemiology and several leading persons from large- scale local and international studies, as well as research consortiums, such as ECRHS (European Community Respiratory Health Survey), ISAAC (International Study of Asthma and Allergies in Childhood), GA2LEN (Global Allergy and Asthma European Network), BOLD (Burden of Obstructive Lung Disease) and GOLD (Global Initiative for Chronic Obstructive Lung Disease), are members of the Assembly. The work of the Assembly increases knowledge about environmental, occupational and lifestyle factors, such as the risks of developing respiratory diseases, and also considers factors that contribute to respiratory health [5]. The Epidemiology Group and the Occupational and Environmental Health Group are deeply involved in these studies. Special interest is paid, among others, to the most important single risk factor for respiratory disease, smoking, and the work of the Tobacco, Smoking Control and Health Education Group focuses on the severe and hazardous effects of active and passive smoking. As a result of the increase in understanding about the importance of the interaction of genes and the environment, a fourth Group, Genes and Environment, recently started activities. One of the most important tasks of the Occupation and Epidemiology Assembly is advocacy. During the presidency of Giovanni Viegi two important advocacy committees were established: the Tobacco Control Committee (TCC) and the Environment and Health Committee (EHC). The TCC was preceded by the Smoking Prevention Committee, established in 1998. The committees work closely with the ERS Brussels office, the ERS Headquarters and the ELF in lobbying for respiratory health in Europe, and worldwide via the World Health Organization (WHO). The Assembly collaborated with WHO in the foundation and management of the Global Alliance against Chronic Respiratory Diseases (GARD). Both committees organise evening sessions at the European Parliament and informative activities for the EC. Another example of the committees’ activities was the EHC initiative to organise the first international conference held by a respiratory society on the health effects of climate change [6]. The Assembly has organised several conferences and task forces, and has produced Monographs and important position papers, among them position papers on the respiratory effects of air pollution and occupation [7, 8]. Recent task force reports include updated recommendations on epidemiological studies of COPD [9] and occupational asthma [10]. Members of the Assembly were also part of the Editorial Boards of both the first and the second editions of the European Lung White Book [2, 4]. Perspectives It is important that healthcare providers and society as a whole know about the prevalence and trends of prevalence and incidence of major disease, including the respiratory diseases. Large-scale population studies are necessary for the calculation of prevalence of, for example, COPD and asthma. Information from registry data is not enough to calculate the prevalence of COPD in society, as under-diagnosis is huge large-scale epidemiological studies that include spirometry are required. The diagnosis of asthma is arbitrary, and irrespective of international guidelines, asthma has in reality been classified differently in many parts of the world, including Europe. Thus, population studies also provide important information about asthma, and international studies allow comparison of prevalence between areas and countries. xv