Lung cancer is the leading cause of cancer mortality in the United States, and its incidence is growing throughout the world. The high morbidity and mortality of lung cancer largely results from the fact that most people are diagnosed with advanced disease, when surgical cures are no longer possible. Although many risk factors have been implicated, the most significant risk for developing lung cancer is clearly tobacco exposure. Tobacco use is currently increasing among specific population groups. It is probable that lung cancer will continue as a major medical and social problem for the foreseeable future.