In the FRG the question of health effects by ambient (outdoor) air pollution is often considered with respect to respiratory diseases in children, especially group syndrome. Therefore, the results of a cross-sectional study in Baden-Württemberg are discussed as an example for the role of "outdoor pollution" at presently observed concentrations. In the study that was performed in Stuttgart, Tübingen/Reutlingen and Freudenstadt, the parents of 8.420 children at the age of 6 years participated (response rate 93%). Their reports on diseases were additionally validated and completed by the paediatricians concerned. The "crude" prevalence for the age group 0-6 years is about 9% each for croup syndrome and obstructive bronchitis. This is strongly influenced by sex, disposition in the family, education and nationality of the parents. In contrast, influences of ambient air pollution are less clear or missing. Pollution measurements on a sufficient spatial scale were only available for Stuttgart, where logistic regression showed after adjustment for the relevant confounders only that croup syndrome was slightly increased in streets with high traffic load. For childhood asthma (prevalence 1.5%) a correlation with traffic-dependent pollutants (NO2, NO, CO) and traffic load is found. These results are compared with those from North Rhine Westphalia, and their limitations are discussed.