© 2017 Elsevier Inc. All rights reserved. The lungs package large folds of epithelium the vast area of which is often compared to half a football field or a tennis court. The extensive airway epithelium provides an efficient gas exchange surface and serves as a physical barrier between the body and external environment. Other epithelial activities, such as mucociliary clearance and immune defense that are necessary to protect the lung from the environment vary along the proximal and distal conducting airways. It is therefore critical to maintain epithelial integrity. The airway epithelium is maintained by tissue-specific stem cells and facultative progenitor cells that stay differentiated in the steady state but proliferate in response to injury. Failure of efficient repair and growth of the airway epithelium can result in persistent mucosal injury and contribute to chronic airway disease pathogenesis. Here, we describe the resident stem/progenitor cells and signaling pathways that drive the repair by these cells after injury to the airway epithelium.