In 51 patients, single metastatic brain lesions were excised. Only 10 (8 of these within the last 1½ years) received postoperative radiation therapy to the brain. More than half of the 51 patients had carcinoma of the lung, the primary neoplasm conceded by many observers to have the worst prognosis; yet 15 survived craniotomy longer than 1 year and 11 were alive at time of review. In addition, 12 other patients with histologically confirmed primary carcinoma, suspected of having intracranial metastatic disease, proved to have nonmetastatic lesions at the time of craniotomy, 9 of which were completely benign. There is thus substantial reason for considering the surgical removal of single metastatic brain tumors, or of lesions suspected to be in this category.It is suggested that the patient with known primary malignant neoplasm, in whom symptoms of central or cerebellar dysfunction arise, be fully investigated for an operable lesion. At least a tissue diagnosis should be made, and preferably surgical excis...