Participants undergo spirometry at baseline. Participants also undergo spiral CT scan at baseline and then at 1 and 2 years. Participants with semi-solid or solid nodules of 5-10 mm or ground glass opacity (GGO) 8-10 mm or those with growth of an existing nodule, development of a solid component in GGO, or a new nodule undergo an additional CT scan at 3 months. Some participants also undergo autofluorescence and white light bronchoscopy and bronchial biopsies.