Background: Airway hyperresponsiveness (AHR) and sensitization to allergens are important risk factors of asthma and their correlation has been speculated. Objective: The aim of this study was to investigate the relationship between sensitization to common allergens and AHR to methacholine in Korean elementary school children. Methods: A modified International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire survey was conducted among 1376 children. Bronchial provocation tests to methacholine, skin-prick tests for 16 common allergens and blood tests for immunoglobulin E (IgE) and the fraction of eosinophils were performed. Results: 212(18.2%) children have AHR ( PC2016mg/mL) and 495(42.7%) showed sensitization to more than 1 allergen. The fraction of eosinophil, total serum IgE and the rate of sensitization to common allergens were higher in AHR positive group than in negative group(4.13%±2.65 vs. 3.48%±2.48, p=0.008, 1.87±0.59 vs. 1.74±0.60, p=0.022, and 54.5% vs. 41.2%, p=0.005, respectively). The risk of AHR of the group showing sensitization to more than 2 allergens (aOR=2.91, 95% CI: 1.62-5.25, p0.001) was higher than the group with sensitization to 1 allergen and group without sensitization. Sensitization to Der. p (aOR=1.80, 95% CI 1.15-2.84) and Der f (aOR=1.71, 95% CI 1.08-2.72) were independent risk factors for AHR. Risk of AHR was increased by increasing sensitizations (p value for trend=0.001). Conclusion: In Korean elementary school children, the risk of AHR is increased while the number of sensitization is increased, and the sensitization to house dust mites is independent risk factors for AHR. In addition, the risk is increased significantly with high IgE and eosinophil fraction. * 본 과제는 서울시의 아토피 프리 서울 프로젝트(Atopy Free Seoul Project)의 지원으로 수행되었음.