The prevalence of asthma in children is increasing worldwide. Although the features of asthma are well documented, defining asthma remains a problem. The clinical definition of asthma does not take into account the concept of airway inflammation. A broader definition that incorporates the inflammatory process, reversibility of airway obstruction, and airway responsiveness needs to be more widely adopted. Bronchial hyperresponsiveness is one of the key features in asthma and it can be documented by using pharmacological or non-pharmacological means. The latter appears to be a more physiological test and more acceptable to children. This article gives an overview of the features of asthma and bronchial hyperresponsiveness and shows how various non-pharmacological bronchial challenge tests can help identify bronchial hyperresponsiveness and thus help diagnose asthma in children.