Lung cancer is the most common cause of cancer-related death in both men and women. There are over 51,000 deaths annually from this disease in Japan. The characteristics of lung cancer have changed for several decades. The incidence of the elderly, adenocarcinoma in histology, and stage I disease continues to increase from year to year. In the 1970s, six randomized trials were carried out to evaluate lung cancer screening in the U.S. and Europe. These studies did not contribute to decrease death rate. They concluded there is no evidence to recommend against lung cancer screening. On the other hand, in Japan, several trials by case-control study demonstrated that chest x-ray screening is associated with earlier detection and improved survival. The conclusions are controversial in two studies. Further investigation will be needed to define the benefit of cancer screening.