Poor results in the treatment of lung cancer have led to the development of several techniques designed to obtain tissue for diagnosis and to determine the feasibility of resection. Although mediastinoscopy has obtained great popularity, we have been dissatisfied with it because of the low yield of positive results and the attendant increases in length of operations and hospitalizations. We have modified the old technique of thoracoscopy, using a sterilized sigmoidoscope inserted through an intercostal space with the patient positioned and prepared for thoracotomy. Although most frequently used in patients with lung cancer, this procedure also has been helpful in patients with coin lesions, mediastinal tumors, and penetrating wounds of the chest. Although we agree that mediastinoscopy is useful in selected patients, we believe that thoracoscopy offers a greater number of patients a reliable means of obtaining the proper diagnosis more efficiently.