BACKGROUND: Few studies have investigated traffic-related air pollution as a risk factor for respiratory infections during early childhood. OBJECTIVES: We aimed to investigate the association between air pollution and pneumonia, croup, and otitis media in 10 European birth cohorts--BAMSE (Sweden), GASPII (Italy), GINIplus and LISAplus (Germany), MAAS (United Kingdom), PIAMA (the Netherlands), and four INMA cohorts (Spain)--and to derive combined effect estimates using meta-analysis. METHODS: Parent report of physician-diagnosed pneumonia, otitis media, and croup during early childhood were assessed in relation to annual average pollutant levels [nitrogen dioxide (NO2), nitrogen oxide (NOx), particulate matter≤2.5 μm (PM2.5), PM2.5 absorbance, PM10, PM2.5-10 (coarse PM)], which were estimated using land use regression models and assigned to children based on their residential address at birth. Identical protocols were used to develop regression models for each study area as part of the ESCAPE project. Logistic regression was used to calculate adjusted effect estimates for each study, and random-effects meta-analysis was used to calculate combined estimates. RESULTS: For pneumonia, combined adjusted odds ratios (ORs) were elevated and statistically significant for all pollutants except PM2.5 (e.g., OR=1.30; 95% CI: 1.02, 1.65 per 10-μg/m3 increase in NO2 and OR=1.76; 95% CI: 1.00, 3.09 per 10-μg/m3 PM10). For otitis media and croup, results were generally null across all analyses except for NO2 and otitis media (OR=1.09; 95% CI: 1.02, 1.16 per 10-μg/m3). CONCLUSION: Our meta-analysis of 10 European birth cohorts within the ESCAPE project found consistent evidence for an association between air pollution and pneumonia in early childhood, and some evidence for an association with otitis media.