The lung is one of the most radiosensitive organs. With increasing use of thoracic irradiation as well as the potential for pulmonary radiation exposure from nuclear and radiologic terrorism, normal lung parenchyma is at risk for radiation-induced lung injury. Radiation causes genetic and macromolecular cell injury through direct effects on DNA as well as indirect effects through lipid peroxidation. The risk of radiation lung injury appears to be best predicted by the dose-volume histogram. Most patients present with a dry, hacking, usually nonproductive cough and dyspnea. Although minimizing the amount of radiation and shielding are the principal methods to prevent radiation lung injury, amifostine reduces the incidence and severity of radiation pneumonitis. Corticosteroids are the principal treatment for radiation pneumonitis. Inhaled corticosteroids and keratinocyte growth factor are future therapeutic agents for the prevention and treatment of radiation lung injury.