Asthma is a chronic inflammatory disease of the airways. Structural alteration of the airways and lung parenchyma, "remodeling", is a recognized feature of chronic asthma and a cause of irreversible airway obstruction. Airway and lung remodeling in asthma involves subepithelial fibrosis, but also alterations of bronchial epithelium, airway smooth muscle cells, myofibroblasts, extracellular matrix, mucous glands, blood vessels and nerves. Defining of morphological changes and correlating them with clinical features of the disease has been a major focus of research over the past decade. The results of these studies are often contradictory and there is still little understanding of the mechanisms underlying lung remodeling in asthma.