A case of a nonspecific esophageal motor disorder associated with muscular hypertrophy, revealed by endoscopic ultrasonography, is reported. A 41-year-old man was admitted to the hospital with chest pain and dysphagia. Manometric studies of the esophagus disclosed prolonged duration of propulsive waves with normal amplitude. Endoscopic ultrasonography showed downward thickening of the esophageal muscular layer; the maximum thickness was found at the lower esophageal sphincter. Thickening of the esophageal wall of unknown etiology has been reported as a diffuse esophageal muscular hypertrophy. Previous cases of diffuse esophageal muscular hypertrophy were diagnosed by autopsy. Some cases involved dysphagia and/or chest pain. Therefore, some of the reported cases of nonspecific esophageal motor disorders may have been associated with diffuse esophageal muscular hypertrophy. Association of the two categories was shown by endoscopic ultrasonography for the first time in the present case. Endoscopic ultrasonography is a useful tool for the diagnosis of the thickening of the muscular layer of the esophagus.