A 58-year-old chronic alcoholism patient, who complained of epigastric discomfort, nausea, and frequent loose stool was diagnosed as strongyloidiasis accompanied by duodenal ulcer. The symptoms first appeared two years ago and aggravated during the recent 3 months, and he lost 4 kg of his body weight. Stool examination revealed rhabditoid nematode larvae, which were confirmed as those of Strongyloides stercoralis after cultivation of them to alariform larvae. At duodenoscopy, duodenal ulcer was found. The patient was treated with albendagole (200 mg, bid, for 14 days) for stronglyloidiasis and with colloidal bismuth sulfate(240 mg, bid, for 6 weeks) for duodenal ulcer. After the medication, the symptoms of loose stool and epigastric discomfort were much improved and he was discharged with no clinical problems. This is an interesting case which suggests that S. stercoralis infection could be related with ulceration of the duodenal mucosa.