A reasonable method to evaluate lung cancer screening program is to measure the reduction in death rate from lung cancer among those randomly allocated to screening program (one-step process). Alternative method is two-step process; step 1 is to measure what proportion of lung cancer patients, can be detected through screening and how early the screening can detected lung cancer patients, and step 2 is to delineate effectiveness of therapy following early detection. Advantages and disadvantages of the two processes were described in view of statistical power and sample size. In addition, a workplace-based screening program using chest X-ray files was mentioned as an example of step 1 of two-step process. The example also included economical consideration of the screening.