The effects of radiation on the lung parenchyma and pleura are well described in the literature. Necrosis of the larynx is a known complication of radiation therapy. Necrosis of a part of the tracheobronchial tree following radiation therapy for bronchogenic carcinoma is likely to occur; however, there is little mention in the English-language literature about such an effect. This report describes four cases with total necrosis of a specific bronchus following radiation therapy for squamous cell carcinoma of the lung. All patients received 5,000 to 6,400 rad (50 to 64 Gy) of external-beam radiation. Two patients presented with massive hemoptysis and two with pneumonia. In all four cases, the patients were found to have, by bronchoscopy, necrosis of the bronchus with the involved lobe of the lung replaced by a large cavity lined by tumor tissue. Diagnosis was made 5 to 7 months after radiation therapy was completed. Three of the patients died of exsanguination within weeks following diagnosis of the complication. We suspect that such necrosis occurs as a consequence of radiation therapy in combination with infection in the set up of squamous cell carcinoma, and is a marker of poor prognosis.