OBJECTIVE Photodynamic therapy (PDT) was used to stop life-threatening hemoptysis from bleeding hereditary telangiectasia in bronchi in a 42-year-old man with a 4-year history of repeated embolotherapies, tracheostomies, and ventilator dependence. At the time of his first PDT, he was 10 days past his third embolotherapy, was being ventilated through a tracheostomy and bringing up 100-200 cc of blood daily, necessitating multiple transfusions of blood and platelets. METHODS Four hours after intravenous injection (60 mg/m2 body surface) of the photosensitizer dihematoporphyrin ether (DHE), bronchoscopy through his tracheostomy showed continuous oozing of non-clotting blood from bronchial vessels in both lung fields, requiring continuous suction. We performed PDT to seven bronchial sites. The 630 nm wavelength light energy to activate the photosensitizer was generated by a tunable dye argon laser system and delivered to the endobronchus through a quartz fiber modified with a 2.5 cm diffusing tip passed through the biopsy channel of the bronchoscope. The light power was 500 mW per cm of diffuser and the light dose was 200 J per cm of diffuser. At the end of the treatments, the bleeding had decreased so as not to require suctioning. The following day we treated three other sites with the same light dose. At this time the only bleeding was from the LUL, which oozed briskly after passing the bronchoscope through it. At the end of the treatment bronchoscopy there was minimal bleeding. RESULTS One week after PDT he was discharged with a tracheosotomy and mechanical ventilator. Four months later his tracheostomy was removed. He remained free of hemoptysis for 26 months when life-threatening hemoptysis recurred. Twenty-two hours after his second injection of DHE, we treated four different endobronchial sites with PDT for bleeding from both the right and left bronchial tree. Sixteen months after his second PDT he remains free of hemoptysis. Three other patients treated for uncontrollable life-threatening hemoptysis for bronchitis have remained free of hemoptysis for 9, 17, and 23 months. CONCLUSIONS Photodynamic therapy causes thromobosis and can control bleeding from small vessels regardless of their location or etiology.