Prognosis of lung cancer is markedly improved when cancers are resected in early stages (particularly in stage I). Previous investigations failed to show benefit with use of chest radiographs or sputum cytologies to screen for lung cancer among high-risk populations. More recently, computed tomography (CT) has been used as a screening technique and appears to detect lung cancer at earlier stages (e.g., stage I) compared with usual clinical practice. However, whether screening CT reduces death from lung cancer has not been clarified. This review examines the problem presented by lung cancer, the issues presented by screening, and the results of past and recent studies of lung cancer screening.