BACKGROUND: Studies of the clinical outcome in adulthood of asymptomatic airway hyperresponsiveness (AHR) to histamine or exercise-induced bronchospasm (EIB) detected in childhood in general population samples are sparse and have produced conflicting results. OBJECTIVE: To describe the outcome of asymptomatic AHR to histamine and EIB. METHODS: Data from a 12-year follow-up study of a random population sample of individuals aged 7 to 17 years at enrollment were analyzed; only individuals without asthma at enrollment were included in the analysis. AHR to inhaled histamine, EIB, lung function, and sensitization to aeroallergens were measured. RESULTS: Among the 281 nonasthmatic participants studied, 58 (22%) had AHR to histamine, 33 (12%) had EIB, and 82 (29%) had AHR to histamine and/or EIB. At follow-up, 37.9% of individuals with AHR to histamine and 30% of individuals with EIB had developed current asthma, compared with only 5% of individuals in whom these test results were negative. In patients with AHR to histamine, parental asthma (odds ratio [OR], 12.6; 95% confidence interval [CI], 1.5-108.5), furred pets ownership (OR, 6.0; 95% CI, 1.2-19.6), and dermatitis and/or rhinitis in childhood (OR, 2.2; 95% CI, 1.1-5.1) predicted the subsequent development of asthma, whereas no risk factors for the development of asthma could be identified in individuals with EIB CONCLUSION: Asymptomatic AHR to histamine and EIB in childhood predict the subsequent development of asthma in adulthood. A genetic disposition to asthma, furred pets ownership, and concomitant rhinitis or dermatitis increase the risk of asthma development in individuals with AHR to histamine.