This is a single center, single arm, non-randomized prospective study. We plan to enroll persons between 50 and 74 years in age, who had cigarette smoking of at least 30 pack-years, and, if former smokers, had quit within the previous 15 years. Persons who had previously received a diagnosis of lung cancer, had undergone chest CT within 18 months before enrollment, had hemoptysis, or had an unexplained weight loss of more than 6.8 kg in the preceding year were excluded.