Although ulcerative colitis (UC) is confined to colonic and rectal mucosa in a continuous fashion, recent studies have also demonstrated the involvement of upper gastrointestinal tract as diagnostic endoscopy becomes more available and technically advanced. The pathogenesis of UC is not well established yet. It might be associated with an inappropriate response of host mucosal immune system to gut microflora. Although continuous and symmetric distribution of mucosal inflammation from rectum to colon is a typical pattern of UC, clinical feature and course of atypically distributed lesions in UC might also help us understand the pathogenesis of UC. Herein, we report a case of duodenal involvement of UC which successfully remitted after infliximab therapy. Endoscopic and pathologic findings before and after administration of anti-tumor necrosis factor suggest that the pathogenesis of upper gastrointestinal involvement of UC may be similar to that of colon involvement.