We observed duodenal erosion in 45 (10.8%) of 418 patients who underwent endoscopic therapy for gastroesophageal varices. Duodenal erosion in patients with portal hypertension was likely to be located in ringed fashion around circular Kerckring's folds, while ordinary duodenitis causes spotty erosive lesions mainly observed in the bulbus. Examination by endoscopic ultrasonography revealed edematous duodenal walls and the structure of proliferated vessels both in and around the duodenal walls. Histological characteristics were dilatation of vessels and edema in the mucosal and submucosal layers. We assume that the decrease in mucosal resistance caused by the congestion associated with portal hypertension is one factor that induce the characteristic erosions in the duodenum. Duodenal erosion in patients with portal hypertension is regarded as one of the lesions accompanying portal hypertensive duodenopathy.