Between 1966 and 1980, 72 patients with operable carcinoma of the lung were treated primarily with radiotherapy because coexisting, nontumor related medical problem, or patient refusal prevented thoracotomy. We compared results obtained in this group with results obtained by thoracotomy in 123 consecutive patients over the age of 70, who were assessed in a similar fashion, but who underwent thoracotomy. All patients in both groups had proven, nonsmall cell carcinoma of the lung without clinical, laboratory, or radiologic evidence of tumor spread. All patients in both groups had a negative staging mediastinoscopy, and bronchoscopic findings consistent with operability. Many of the patients treated with radiotherapy had less than a curative dose as their general medical condition prevented a course of radical radiotherapy. It is apparent, however, that the results of radiotherapy for patients with operable carcinoma of the lung may be disappointing and that for patients who are marginal in terms of operative risk, the benefits of surgical resection may warrant the risks involved.