This paper is to reconsider and reorganize surgical indication of metastatic tumor in the lung in accordance with the recent progress of medicine, which was based on the patients experienced at National Cancer Center Hospital. Among several criteria proposed by Thomford in 1965, three items: 1) the patient is a good risk for surgery, 2) the primary malignancy is controlled, 3) the lung is the only one site for metastatic lesion, remain to be true even today. In addition, another three conditions must be recognized in selecting patients: 1) Biological behavior of the tumor varies in different histology and different site of the primary lesion. 2) When the tumor is susceptible to chemotherapy, surgical indication can be widen. 3) The tumors located in bilateral lung, which used to be surgically contraindicated, can be successfully removed with simultaneous thoracotomy via sternotomy.