THE AUTHORS OBSERVED one case of an iatrogenic subarachnoid-pleural fistula secondary to the resection of an upper lobe carcinoma of the lung. The clinical presentation was characterized by a sudden deterioration of mental status and level of consciousness immediately after the removal of the thoracotomy chest tube. The diagnosis was substantiated by the demonstration of pneumocephalus by a computed tomographic scan of the head and by the identification of a left T5 nerve root fistula by a postmyelographic computed tomographic scan. The excellent anatomical definition achieved by this modality emphasizes its usefulness in the identification and therapeutic management of these lesions. Operative treatment consisted of the suture ligature of the nerve root and a chest drain. The postoperative course was uneventful, and the outcome was excellent, with the only finding of sensory loss in the T5 nerve root territory. A review of the literature disclosed 11 similar cases, with some differences in the choice of the most appropriate diagnostic procedure and significant differences in the therapeutic options, which were related to the various mechanisms of injury.