In order to assess the relationships of air pollution to ventilatory function and to the prevalence of respiratory symptoms, a French national survey was conducted from 1974 to 1976 in 28 areas located in 7 cities (Bordeaux, Lille, Lyons, Mantes, Marseilles, Rouen, Toulouse) and a newly industrialized region (Fos-Berre). The following pollutants were measured : SO2 (specific and acidimetric methods), suspended particulates (gravimetric method and smoke), NO2 and NO. Subjects were men and women, not manual workers, aged 25-59, and children aged 6-10. Ventilatory function was measured with a dry expirograph (Vitalograph) and respiratory symptoms were obtained from a standardized questionnaire. There were large variations between areas in the measured pollution concentrations. The extreme values were, for SO2 (specific) 22 and 85 microgram/m3, for SO2 (acidimetric) 13 and 127 microgram/m3, for suspended particles (gravimetric) 45 and 243 microgram/m3, for suspended particles (smoke) 21 and 152 microgram/m3, for NO2 12 and 61 microgram/m3 and for NO 7 and 140 microgram/m3. 19191 subjects were examined (7581 men, 9083 women, 1291 boys and 1236 girls). Besides the well known relationships of age and smoking to ventilatory function and the prevalence of respiratory symptoms, less well established results appeared, in particular the importance of moderate work-related exposure. The influence of pollution will be the subject of the second part of this work.