The European Community Respiratory Health Survey is an international multicenter cohort study of asthma, allergy, and lung function that began in the early-1990s with recruitment of population-based samples of 20- to 44-year-old adults, mainly in Europe. The aims of the study are broad ranging but include assessment of the role of in utero exposure to tobacco smoke, exposure to environmental tobacco smoke, and active smoking on the incidence, prevalence, and prognosis of allergy and asthma. Cross-sectional and longitudinal analyses looking at these associations have been conducted, sometimes only using information collected in one country, and on other occasions using information collected in all the participating centers. This article summarizes the results from these various publications from this large epidemiologic study.