Tracheobronchial amyloidosis is characterized by deposits of amyloid in airway walls. No effective treatment is known. We describe a 59-year-old woman who presented with increasing symptoms of airway obstruction due to diffuse deposition of amyloid throughout her tracheobronchial tree. She was treated with external-beam radiation therapy (20 Gy) with marked improvement in her symptoms, effort tolerance, bronchoscopic appearance, and forced expiratory volume in 1 second (1.39 L to 1.97 L [42%]). This improvement was maintained during 21 months of follow-up.