Thirty-five patients with tumors within the tracheobronchial tree were treated with photoradiation therapy (PRT) employing the photodynamic action of hematoporphyrin derivative (HPD). An effective protocol has been developed consisting of 3.0 mg/kg HPD given intravenously 72 hours prior to the bronchoscopic illumination of the endobronchial tumor sites with red light (630 nm) from an argon pumped dye laser. Light applicators were developed that provided surface (area) and insertion (volume) illumination of tumor masses. Average light dosages of 100 J/cm2 and 200 J/cm were used for surface and insertion illumination, respectively. Delivery rates were 200 mW/cm2 and 400 mW/cm. There was no immediate visible effect such as coagulation or charring noted. All malignant endobronchial tumors responded. Tumors included primary and metastatic lesions of various histologic types. Response was complete for tumor within the bronchus after one treatment in 80% of instances. The remaining cases required two treatments to obtain a complete response due to the extensive length of bronchus involved or because multiple sites were present. A complete response, that is, the full opening up of the lumen to the bronchial wall, was accomplished in all but one instance. Atelectatic lungs or lobes were re-expanded and reaerated. Dyspnea and cough became significantly less. The follow-up achieved to date indicates improvement in symptoms, activity level, and the return to work in a significant number of cases.