Lung cancer remains the most common cause of death due to neoplasm in the United States. Despite recent efforts, early diagnosis provided through screening studies has not resulted in improved survival. Most lung cancer victims are symptomatic at presentation, and 50% have distant metastases. The diagnosis, often suspected on plain chest radiograph, can usually be confirmed with bronchoscopy or sputum cytology. The most useful routine staging evaluation, in addition to history and physical examination, is computed tomography. The routine use of other staging modalities is not recommended. A new staging system, currently in use throughout North America, western Europe, and Japan, permits accurate estimation of prognosis and assignment to therapeutic groups.