The correlations between the concentrations of several air pollutants (sulphur oxides, suspended particles, nitrogen oxides) and ventilatory function and the prevalence of respiratory symptoms in 20 areas located in six French cities showed the following results : a) among adults of both sexes, the air concentration of SO2 is associated with the prevalence of lower respiratory symptoms, b) among children it is associated with the prevalence of upper respiratory symptoms, c) in both adults and children, the higher the SO2 pollution, the lower the forced expiratory volume in one second, d) no other pollutant is associated with ventilatory function and the prevalence of respiratory symptoms. The methods and results of this study are discussed and compared with those of other studies.