Echinostomiasis is an endemic intestinal trematodiasis of humans in Korea. We observed a human case of Echinostoma hortense infection who had ulcerations on the duodenal mucosa. A 55-year old man living in Hamyang-gun, Kyongnam, complained of epigastric pain with hematemesis in April 1994. Endoscopy revealed lesions of early gastric cancer and duodenal ulcerations. A penetrating parasite into the duodenal mucosa was picked out, and identified as E. hortense. As the patient was treated with praziquantel 10 mg/kg single dose, 3 more E. hortense and 7 Metagonimus worms were recovered. This case demonstrates that echinostomiasis causes gross ulcerations in the duodenum.