Gastro-intestinal stromal tumors (GISTs), as currently defined, represent the largest category of primary non epithelial neoplasms of the gastrointestinal tract. They arise from mesenchymal cells located in the wall of the organ and show a remarkable variability in their differentiation pathways. For this reason there is relevant degree of confusion in their interpretation. On the basis of immunohistochemical and ultrastructural studies these neoplasms are divided into several categories: leiomyomas, schwannomas and less differentiated tumors referred as GIST. In the small bowel GIST are uncommon. Usually asymptomatic, they could be the cause of surgical emergencies like massive bleeding, obstruction, intussusception or perforation. Generally benign, an higher percentage of malignant cases are described in the small bowel. The Authors report a case of malignant GIST of the small intestine presented with bowel obstruction by ileal invagination. In this case, as usually it happens in malignant GIST, the final diagnosis was obtained by an abdominal surgical exploration.