the paper describes two new endoscopic signs which can be useful in the use of diagnostic bronchoscopy. this is an essay on particular anatomic and functional circumstances suggesting the presence of a pathology which cannot be seen by the bronchoscopist. these two signs are the bubble sign and the black hole sign. the bubble sign is observed when the airflow is absent in a subsegmental bronchus leading to a peripheral pulmonary mass. this can be shown by the lack of mobile bubbles when a subsegmental bronchus is flooded with saline solution. the black hole sign consists in the circular penumbra observed at the end of a bronchus which communicates with a cavity. the paper describes the presentation and interpretation of these signs and offers an explanation about their physiopathology.