Although numerous gastrointestinal endoscopes pass through the oropharynx and the hypopharynx, it is extremely difficult to detect an early cancer in these sites during routine endoscopic examination. Most patients with cancer in these sites are usually diagnosed in advanced stages. If effective screening methods can detect an earlier stage, such as carcinoma in situ, it would obviously be of great benefit. Narrow band imaging is an innovative optical technology that can clearly visualize the microvascular structure of the organ surface. Herein, we demonstrate that narrow band imaging combined with magnifying endoscopy can identify a carcinoma in situ in oropharyngeal and hypopharyngeal mucosal lesions. Scattered irregular foci of microvascular proliferation projecting to the dysplastic squamous epithelium are the typical features. These results indicate that an approach to visualize angiogenesis or morphologic changes of microvessels in the superficial neoplasm can be a new diagnostic method not only for the head and neck region but also for other sites in the gastrointestinal tract.