The aim of this study was to investigate the relationship between air pollution and respiratory symptoms in young children. A total of 263 children at high risk of developing asthma or atopy were recruited antenatally and all respiratory symptoms experienced by the children were recorded by their parents for five years. Daily pollutant concentrations and meteorological data (ambient temperature and humidity) were collected from network monitoring sites. Logistic regression models investigating relationships between individual air pollutants and respiratory symptoms showed significant associations between Ozone (O3) (1 h and 8 h) concentrations and raised body temperature (lag 0); Carbon monoxide (CO) (8 h) and wheeze/rattle and runny/blocked nose (lag 5 and additive exposure over 5 days); Nitrogen dioxide (NO2) (24 h) concentrations and cough (lag 0 and additive exposure over 5 days) and PM2.5 and visibility (BSP) (1 h) with cough (lag 0). These associations were observed even though air pollutant concentrations were below national standards throughout the study period.