The precise, accurate diagnosis of malignant airway invasion is essential to determine the likelihood of complete resection and survival of patients with invasive carcinoma of the upper esophagus. The usefulness of ultrasonic scanning of the tracheobronchial wall by bronchoscopic ultrasonography (BUS) was studied, and results were compared with those of computed tomography (CT). Sixty-six consecutive patients with advanced squamous cell carcinoma of the upper esophagus treated from 1997 to 2000 were studied. The presence of tracheobronchial invasion was diagnosed by BUS based on an interruption in the most external hyperechoic layer of the tracheobronchus (corresponding to its adventitia). BUS was completed without any complication in all patients. The accuracy of diagnosis was validated intraoperatively, and it was better for BUS (90%) than for CT (62%) ( p = 0.001). Of the 26 patients diagnosed as being invasion-free by BUS, only 2 had invasion, compared to 7 of 22 patients who had invasion after CT scans had suggested they did not. Survival was worse for patients diagnosed as having invasion than not having it based on CT scans ( p = 0.0071), but the difference was more significant with BUS ( p < 0.0001). BUS is a safe, reliable staging modality for cancer in the upper esophagus. When surgery is considered, BUS is essential for determining whether a curative resection is possible.