Diagnostic pleuroscopy has been performed under local anesthesia in nine patients using a gas sterilized flexible fiberoptic bronchoscope inserted through a 1 to 2 cm chest incision into the pleural space. Pleuroscopy in one patient excluded recurrent neoplasm on the pleural aspect of a bronchopleural fistula. Another patient had a pleuroscopic biopsy of the lung, which was the only method successful in diagnosing a metastatic renal carcinoma. The other seven patients were studied for pleural effusions which were undiagnosed after study of pleural fluid and/or Abrams needle biopsy. In four of them pleural implants of carcinoma were visualized and proved by biopsy. Three patients had negative pleuroscopy, two of these also being negative at subsequent thoracotomy. One was not explored because of extrathoracic metastases. The procedures were performed with minimal patient discomfort and no serious complications.