Rationale: Although short-term exposure to air pollution has been associated with acute, reversible lung function decrements, the impact of long-term exposure has not been well established. Objective: To evaluate the association between long-term exposure to ozone (O₃), particulate matter <10 µm in diameter (PM₁₀) and nitrogen dioxide (NO₂) and lung function growth in Mexico City schoolchildren. Methods: A dynamic cohort of 3,170 children aged 8 years at baseline was followed from April 23, 1996 through May 19, 1999. The children attended 39 randomly selected elementary schools located near 10 air quality monitoring stations and were visited every 6 months. Statistical analyses were performed using general linear mixed models. Results: After adjusting for acute exposure and other potential confounding factors, deficits in FVC and FEV₁ growth over the 3-year follow-up period were significantly associated with exposure to O₃, PM₁₀ and NO₂. In multi-pollutant models, an interquartile range (IQR=11.3 ppb) increase in mean O₃ concentration was associated with an annual deficit in FEV₁ of 12 ml in girls and 4 ml in boys, an interquartile range (IQR=36.4 µg/m³) increase in PM₁₀ with an annual deficit in FEV₁ of 11 ml in girls and 15 ml in boys, and an interquartile range (IQR=12.0 ppb) increase in NO₂ with an annual deficit in FEV₁ of 30 ml in girls and 25 ml in boys. Conclusion: We conclude that long-term exposure to O₃, PM₁₀ and NO₂ is associated with a deficit in FVC and FEV₁ growth among schoolchildren living in Mexico City.