Background: Airway obstruction due to blood clot occurs unusually but in a variety of clinical settings. Initial efforts for removal of the endobronchial blood clot involve flexible bronchoscopic evaluation with saline lavage and suctioning and then forceps extraction. If unsuccessful, further options include rigid bronchoscopy, Fogarty catheter dislogement of the clot, and topical thrombolytic agents. The several successful uses of endobronchial streptokinase or urokinase to dissolve an endobronchial blood clot have been previously reported, but not yet in Korea. Herein we describe a 51-year old man with superior vena cava thrombosis secondary to Behcet's disease who experienced life threatening airway obstruction after hemoptysis due to a large organized blood clot in left main bronchus. Urokinase(260,000 U), injected through a fiberoptic bronchoscope, totally dissolved the clot. No complications occured.