Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease of unknown cause characterized by progressive scarring of the lung parenchyma and relentless loss of lung function. The diagnosis depends on close collaboration between clinicians, radiologists, and pathologists. No therapies approved by the Food and Drug Administration are available for IPF, and an analysis of completed clinical trials has demonstrated that the clinical course of IPF is largely unpredictable. Until therapies that improve survival become available, measures to preserve function and quality of life should be considered, and gastroesophageal reflux should be treated aggressively. © 2012.