Introduction - Emergency department (ED) visits for asthma are largely preventable, and ED data, when combined with hospitalization data, are useful for monitoring asthma. The objective of this study was to describe ED visits for asthma in the Île-de-France region. Methods - The study examined asthma-related visits among children aged 2–14 and young adults (15–44 years) in 20 EDs in the Île-de-France region that participated in the Oscour network in 2006–2007. Results - Visits for asthma accounted for 3.5% of pediatric visits and nearly 1% of young adult visits. One-quarter of children and 17% of adults were hospitalized. Among adults, two major peaks in asthma-related visits were observed in June–July 2006. Among children, an increase in asthma-related visits was noted at the start of the school year in September. Discussion - This study documents the occurrence of exceptional events that resolved rapidly and coincided with thunderstorms during the pollen season. In children, the September epidemic of asthma exacerbations appears to be linked to the resurgence of respiratory infections as children returned to group settings. (R.A.)