Twenty-four patients underwent single and multiple carbon-dioxide laser treatments for endobronchial lesions at the Mount Sinai Hospital in Toronto. Fifteen had malignant disease, 2 had benign tumours and 7 had benign strictures. Rigid bronchoscopy with Venturi ventilation was used in all, with the CO2 laser therapy directed down the open end of the bronchoscope. In the majority of cases laser therapy was combined with mechanical débridement, consisting of removal with biopsy forceps and use of the end of the rigid bronchoscope to "core out" the tumour mass. Assessments were made subjectively by the patient and objectively by bronchoscopic examination and post-treatment roentgenography. Worthwhile improvement was noted in patients who had proximal malignant lesions and those with benign lesions at all levels. Overall there was an effective improvement in 18 of the 24 patients.