We report a case of phlebosclerotic colitis with deep circumferential ulceration in which the characteristic findings were observed radiologically and endoscopically. Previously, the patient was diagnosed with colitis of unknown etiology in 1999 when a colonoscopy showed small erosions, ulcers, and dark purple mucosa in the right colon. As a result of parenteral nutrition treatment, his symptoms and ulcerations disappeared; however, the dark purple mucosa remained unchanged for three years on the annual endoscopic follow-up. Recurrent colitis associated with circumferential ulceration was diagnosed in 2002. The patient was treated again with only parenteral nutrition and his symptoms improved after a few days; the ulceration completely disappeared within seven months. This case emphasizes the benefit of nonsurgical treatment for phlebosclerotic colitis even in cases of deep circumferential ulceration.