The epithelial cells that line the lung are critical in lung disease because they are the first to encounter inhaled pollutants. Their initial responses to injury and inflammation govern subsequent responses of other pulmonary and inflammatory cell types that may result in disease causation or repair from injury. The signaling pathways elicited in epithelial cells and their relationship to cell death (apoptosis), proliferation, inflammation and fibrosis are the emphases of this Program Project grant (P01HL67004) awarded by the National Heart, Lung and Blood Institute of NIH.