Asthma pathophysiology involves bronchial hyperreactivity, inflammation and remodelling, these features being closely linked. Bronchial hyperreactivity is characterized by an excessive airway response to a wide range of stimuli. Bronchial inflammation is characterized by an infiltration of all layers of the bronchial wall by a variety of inflammatory cells, especially mast cells, lymphocytes and eosinophils. Bronchial remodelling is defined by various structural alterations of all components of the bronchial wall, which is responsible for a worsening of the disease.