Asthma is a heterogeneous disease that frequently shows progression of airway obstruction. There are indications that ongoing airway inflammation is responsible for the more severe hyperresponsiveness, lower lung function, and accelerated loss of forced expiratory volume in 1 second. At this moment, we are not well informed about the contributing factors to and the exact relation between airway inflammation and airway remodeling. Exciting new findings during the past years are the potential role of interleukin-13, the further exploration of the epithelial-mesenchymal trophic unit, and the presence of degranulated mast cells in smooth muscle bundles from the bronchi.