One hundred and sixty-five patients of choriocarcinoma were treated during the period from 1957 to 1979. Pulmonary metastases were found in 111 of the 165 patients. The authors found that surgical intervention for pulmonary metastasis was an extremely effective means for the patients who were not cured by chemotherapy and satisfied the criteria that we newly established for surgery. All patients satisfied the criteria achieved primary complete remission and their three years survival rate was 80%. The timing for surgery was also discussed and it was concluded that pulmonary surgery should be adopted when patient's urinary hCG values persisted at the level below 1000 iu/l for 70-80 days period.