Carcinoma of the bronchus in recent years has become a problem of major importance. It is now known that primary carcinoma of the lung, which almost always arises in a bronchus, constitutes between 5 and 10 per cent of all carcinomas.1In frequency, therefore, it is comparable with carcinoma of the large intestine, and it is much more frequent than the malignant tumors of some other organs that have received much more comment. The problem of primary carcinoma of the lung is of special importance, since up to the present time at least the prognosis has been almost uniformly bad because of the complete futility of any methods of treatment other than surgical excision. There is no record in the literature of the successful treatment by radiotherapy of a single case in which the pathologic evidence has been incontrovertible and in which a five year interval without recurrence has