1. To determine the rates of various follow-up diagnostic procedures in the periods before and after various screening results, with the emphasis on specific abnormal, not suspicious for lung cancer, findings (e.g., COPD, scarring, cardiac abnormalities). 2. To ascertain whether rates for certain procedures are increased in the period after a given abnormal, not suspicious for lung cancer, screening result as compared to the period after a negative screening result or as compared to the period before the abnormal, not suspicious for lung cancer, screening result. 3. To estimate medical costs in the periods before and after various abnormal, not suspicious for lung cancer, screening results as compared to comparable periods before and after negative screens.