Of five patients with epidermoid carcinoma of the lung who were treated with small fields of 80 Gy in 40 fractions/8-11 weeks (TDF123-129) to the hilar region, four patients developed marked stenosis of the proximal bronchi without tumour progression and died of pulmonary insufficiency 1-3 years after radiotherapy. These results should serve as a warning against escalation of the radiation dose, and the upper optimal dose might prove to be less than 80 Gy for the treatment of pulmonary hilar lesions.