Mediastinoscopy was reviewed in a series of 36 patients suspected of having resectable carcinoma of the lung. Results of mediastinoscopy in nine cases were positive, thus eliminating the need for an exploratory thoracotomy. Of the 27 patients with negative results, six were found to have unresectable carcinoma due to mediastinal involvement beyond the reach of the mediastinoscope. The procedure is done with the patient under general anesthesia in conjunction with bronchoscopy. There was no morbidity and very little discomfort, enabling discharge from the hospital within 24 hours. In contrast, exploratory thoracotomy carried a morbidity including a 33% reduction in vital capacity and 22% reduction in total lung capacity. Mediastinoscopy, as a mode of selectivity, avoids significant operative risks, and assures preoperatively a better chance of cure for the patient with suspected carcinoma of the lung.