The term gastrointestinal stromal tumor describes a heterogeneous group of tumors of mesenchymal origin with particular histologic features. Their classification has recently been made possible thanks to numerous immunohistochemical and ultrastructural studies. We report the case of a patient who came to our attention because of serious anemia due to a gastrointestinal stromal tumor located between the second and third portion of the duodenum. This pathology, although not frequent, should be considered in the differential diagnosis of gastrointestinal bleeding. In these cases it is important to perform careful endoscopic inspection to the third portion of th duodenum, even when previous tracts evidence lesions that could be responsible for the patient's symptoms.