Airway remodeling is a characteristic feature of asthma that leads to chronic irreversible airway obstruction. Fibrosis in the basement membrane region is a hallmark of remodeling in asthma that is not found in other diseases. In the outlined studies, we investigated the relationship between relaxin and airway fibrosis in asthma using acute and chronic models of allergic airway disease. These studies confirm a critical role for relaxin, in the regulation of collagen deposition in the airway/lung in animal models of allergic airway disease.