Isolated phlebitis of the gastrointestinal tract is rare and potentially life threatening. We report on a patient who developed peritonitis, requiring emergency laparotomy, total colectomy, and ileostomy because of colon necrosis. The specimen displayed multiple ulcerations and erosions. Histology showed a predominantly lymphocytic infiltrate of small-sized and middle-sized veins in the submucosa and subserosa, associated with granulomas and foci of vein wall necrosis. Arteries were spared. No local recurrence or systemic vasculitis developed during a follow-up period of two years. Isolated granulomatous phlebitis seems to be self-limited, and its cause is unknown. Surgical resection of the diseased intestine is usually curative.