Two unusual cases of pleomorphic adenoma (benign mixed tumor) of the trachea were found in a 56-year-old woman and a 20-year-old man. Both patients had been initially treated for presumed bronchial asthma for 5 years and 4 years, respectively. Pulmonary function tests in each showed typical extrathoracic obstruction. The diagnosis of tracheal lesions in both cases was based principally on the following: 1) dyspnea without complete remission over an extended period of time following initial examination; 2) marked retraction of the supraclavicular and suprasternal notches during inspiration with stridor on physical examination; and 3) a high degree of suspicion. Large tumors were found within the air column of the trachea by soft tissue density X-ray films and electroradiographs of the neck, CT scans of the neck and mediastinum in each patient revealed that the tumor originated from the membranous layers of the trachea in the woman and the posterolateral wall of the trachea in the man. Fiberoptic bronchoscopy confirmed the clinical diagnosis. Both cases were successfully treated by segmental resection of the trachea with end-to-end anastomosis.