One hundred cases of metastasis to lung or mediastinum from an extrathoracic source were reviewed. Fifty-nine patients were considered inoperable following initial investigation, eight were unresectable at thoracotomy, and eight had palliative resections or resection prior to control of the primary. None of these survived beyond 26 months. Twenty-five patients had resections for cure, with a fiveand ten-year survival of 47% (9 of 19 survivors) and 25% (3 of 12 survivors), respectively. Criteria for selection included control of the primary lesion with metastases limited to one lung. Best results were obtained when pulmonary metastases were detected more than one year following control of the primary lesion. About 5% of all patients with visceral malignancy manifest a pulmonary metastasis which should meet these criteria. Resection is possible with a low operative mortality (3%) and a prognosis often better than with bronchogenic carcinoma.