Background: There is little information about the prevalence of asthma in Latin American children. Aim: To determine the prevalence of asthma among Chilean school age children. Subjects and methods: The prevalence of respiratory symptoms related to asthma in schoolchildren aged 7 and 13 years, coming from South Santiago, Central Santiago, Valdivia and Punta Arenas, was determined using the methodology of the International Study on Asthma and Allergies in Childhood (ISMC). A random sample of school children aged 6-7 and 13-14 years from each locality was selected. This resulted in 24)470 surveyed children (11,723 aged 6-7 years and 12,747 aged 13-14 years). Results: The current prevalence of wheezing ("wheezing in the last 12 months") ranged from 16.5% to 20.ó% in children aged 67 years, and from 6.8% to 11.7% in children aged 13-14 years. The cumulative prevalence of asthma ("asthma ever"), ranged from 9.7% and 16.5% in the 6-7 years group and from 7.3% to 12.4% in those aged 13-14 years. Conclusions: This study found much higher figures for prevalence of respiratory symptoms related to asthma in school children than those previously reported in this country, with a significant variability between centers (p<0.05). The prevalence of asthma in Chilean schoolchildren is as high and variable as that reported in industrialized countries