Between November 1988 and March 1990, 24 patients with endobronchial tumors that had recurred after external beam radiation therapy were treated with high dose rate intraluminal irradiation. A remote afterloading high dose rate unit was used, and most patients received two endobronchial treatments, separated by a two week interval. All patients were given the same dose and dose specification to assess the feasibility and complications of the therapy. At each treatment, 15 Gy were delivered with dose specified at a radius of 6 mm from the center of the source, which corresponds to a dose of 9 Gy at a radius of 1 cm. Overall, 21 of 24 patients (88%) showed good symptomatic improvement. Of 18 patients whose chest x-ray showed evidence of collapse or atelectasis caused by tumor obstruction, 15 (83%) had evidence of reaeration. The median duration of palliation, marked by symptoms or a chest x-ray that worsened, was 26 weeks, the range varying from seven to 40 weeks. No patient died as a result of therapy and only one had a complication, bronchospasm, which responded well to bronchodilators. One patient died of hemoptysis approximately three months after treatment. Five additional patients, who were treated off protocol because they had an Eastern Cooperative Oncology Group performance status of greater than two, also received endobronchial irradiation. All five died within one month from worsening pulmonary disease, and we do not recommend endobronchial irradiation for patients with an Eastern Cooperative Oncology Group performance status of greater than two. We conclude that high dose rate endobronchial brachytherapy effectively relieves the symptoms of endobronchial obstruction due to recurrent lung cancer and can be given safely as an outpatient procedure. As the complications were minimal in this series treated with a uniform dose of 15 Gy per treatment, future studies should aim at determining the maximum tolerated dose. This technique may also be helpful as a boost after maximal external beam irradiation or to open up areas of atelectasis prior to external beam irradiation.