Airway remodelling refers to changes in the airway structure and includes subepithelial fibrosis, increased smooth muscle mass, submucosal gland enlargement, neovascularisation and epithelial alterations. Remodelling is observed in response to chronic injury and is seen not only in asthma but in all airway diseases. Remodelling is associated with more severe airflow obstruction and airway hyperresponsiveness in asthma; however, the clinical significance of this is still a matter of debate. Research should be pursued to better understand the accurate implication of airway remodelling in disease and its therapeutic modulation. To allow research in this field, accurate and standardised methods should be utilised to measure airway alterations in disease and following therapy. The standard detection of structural alterations is through direct analyses of airway tissues obtained during a post mortem, surgically or by flexible bronchoscopy. To avoid invasive techniques, other tools have been developed to indirectly measure remodelling, including induced sputum, bronchoalveolar lavage fluid, blood and urine analyses, physiological and radiological assessments, as well as in vitro techniques. Although of great interest, the exact significance of airway remodelling measurements gained through such indirect techniques is uncertain and further research is needed. Despite their invasive nature, direct methods should be favoured to adequately measure airway remodelling in disease and its modulation by therapy.