To evaluate the influence of endobronchial laser resection on survival and the pattern of failure in patients with bronchial malignancies, we investigated 75 patients prospectively. These patients had radiation therapy (mean external dose, 53.1 Gy) and endobronchial laser resection to treat an inoperable or recurrent bronchial carcinoma occluding a major airway. Complete recanalization was achieved in 36 percent, partial recanalization was achieved in 51 percent, and no recanalization was achieved in 13 percent. These 75 patients were matched retrospectively with a group of 75 patients who received external radiation therapy because of the same indications, but because of endobronchial compression of a major airway by the tumor, received no laser resection. The patients were matched for age, sex, TNM-status, histologic features, external radiation dose and fractionation, lung resection, cytotoxic therapy, and brachytherapy; they were treated in the same period. The incidence of terminal hemorrhage was four times higher in patients who received endobronchial laser resection (34.5 percent) compared with those who did not (7.7 percent). Successful laser reopening of a major airway influenced the pattern of failure: with full recanalization the cause of death in 23.3 percent of cases was respiratory failure and in 26.7 percent, terminal hemorrhage; whereas with no recanalization these figures were 56.3 percent and 18.8 percent, respectively. Laser resection did not influence overall survival, but in patients with full reopening of a bronchus, the time interval from treatment to death was prolonged by more than 4 months compared with those patients in whom recanalization failed. Comparing our observations on the immediate cause of death with reports in the literature, we conclude that the higher percentage of terminal hemorrhage in patients receiving endobronchial laser resection is not directly related to the treatment, but reflects different patterns of tumor growth with respect to mucosal destruction not covered by the TNM system.