A 57 year old woman, affected by Ulcerative Colitis (UC) in remission, was admitted to our unit with a history of episodic melena and progressive anemia. Computed tomography (CT) of the abdomen revealed a solid mass in the upper left pelvic cavity. After surgical laparotomy, the mass showed histological characteristics of a gastro intestinal stromal tumor. This report describes a GIST in a patient with extensive UC, which was in remission at the time of diagnosis. To our knowledge, this is the first report of an association of this type.