Background: Many institutes are interested in lung metastatectomy than before because of the improved long term survival, low mortality, and low morbidity after lung metastatectomy. However, prognostic factors affecting long term survival are controversial. We attempt to analyze the prognostic factors affecting retrospectively by comparing the results of lung metastasectomy. Material and Method: Between Jan. 1990 and Dec. 1997, 74 operations were taken in 63 patients with pulmonary metastases in various primary sites. We analyzed the postoperative long term survival according to sex, cell type, laterality, disease free interval(DFI), operation, the number of metastases, and the size of the largest metastasis. Result: There were 27 male and 36 female patients. Sex did not appeared to affect survival time(p=0.849). The primary tumor was carcinoma in 32, sarcoma in 28, and others in 3. Cell type, considering carcinoma and sarcoma, did not relate to survival time(p=0.071). DFI had no influence on the outcome(p=0.902). The type of operative procedure had no influence on the outcome(p=0.556). The laterality of metastases, 47 unilateral(74.6%) and 16 bilateral(25.4%), had no influence on the outcome(p=0.843). The number of metastases excised(one, two or three, four or more) did not appear to affect survival(p=0.263). The size of largest metastasis(<=10mm, 11mm-30mm, and >30mm) did not appear to affect survival(p=0.751). Previous factors were evaluated in both the carcinoma and sarcoma patients respectively. DFI was the only significant prognostic factor in metastatic lung sarcoma(p=0.0026). Conclusion: Survival was not related to sex, cell type, laterality, DFI, operative procedure, number of metastases, nor the size of the largest metastasis. DFI was related to the survival time in sarcoma group but further study is needed.