In the United States, lung cancer is now the leading cancer killer among men, and it will soon be the leader among women. Most lung cancers are attributable to cigarette smoking. Symptomatic lung cancer tends to be advanced and unresectable. Chest roentgenography and sputum cytology are the only techniques proved capable of detecting presymptomatic, early-stage disease. Treatment of lung cancer depends primarily on the cell type and the extent of the tumor. Small cell cancer tends to be widespread, and the favored treatment is combination chemotherapy. For non-small cell cancer, the treatment of choice, whenever possible, is surgical resection. Efforts directed toward early detection and treatment have failed to reduce lung cancer mortality substantially. Thus, primary prevention through control of cigarette smoking remains the single most important measure for combating this frustrating disease.