The complications associtaed with gastrectomy include dumping syndrome, duodenogastric reflux, gastroesophageal reflux, and excretion disorders of the stomach. Reflux esophagitis, which occurs after cardiac gastrectomy, is thought to be caused by duodenogastric reflux, and is difficult to cure. In this report we describe a case of postoperative reflux esophagitis, where we evaluated the gastric motility disorder and duodenogastric reflux with color Doppler ultrasonography. A 27-year-old male, who underwent cardiac gastrectomy in an operation to remove a gastric ulcer nine years ago, was referred to our hospital complaining of heart burn and chest pain in spite of taking H2-blockers. An endoscopic examination revealed severe reflux esophagitis and a stationary pyloric ring. Suspecting gastroduodenal motility disorders, we had the patient drink 400 ml of consomme soup, and then performed color Doppler ultrasonographic examination, evaluate the duodenogastric reflux. The color Doppler ultrasonographic examination revealed a dilated duodenum, and clearly demonstrated blue images flowing from the antrum to the duodenal bulb. In addition to the normal blue signals, the duodenogastric reflux was demonstrated in red signals, pulsing 21 times every five minutes. These signals were unexpectedly wide, and we suspected a functional disorder of the pyloric ring. Also, because reflux esophagitis appeared to be caused by the duodenogastric reflux, we began oral administration of protease inhibitors in addition to the proton pump inhibitor to cure this alkali esophagotis. Eight weeks after treatment began, esophagitis improved endoscopically and clinically. We therefore conclude that color Doppler ultrasonographic examination is a useful new method for diagnosis of duodenogastric motility disorders including both duodenogastric reflux and dumping syndrome.