BACKGROUND: Previous studies suggest a relationship between air pollutants, aeroallergens, and asthma exacerbations. OBJECTIVE: To simultaneously examine the role of seasonality, air quality, aeroallergens, and climate on asthma-related pediatric emergency department (ED) visits. METHODS: A retrospective 4-year study of asthma-related ED visits was conducted. RESULTS: September had the highest number of visits (p < 0.01). There were lower temperatures and precipitation (p < 0.01) and higher tree and weed pollen levels (p Euro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin) 0.05) on days with more visits (p Euro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin) 0.05), while grass pollen, mold, ozone, NO2, and PM2.5 levels showed no significant differences. Conclusions: Asthma-related visits were associated with aeroallergens and climatic factors and not air-quality factors.