Although the small bowel accounts for 75% of the gastrointestinal length and 90% of its absorptive surface, neoplasms of this organ, both benign and malignant, are relatively rare. These tumors represent less than 10% of all gastrointestinal tumors, 1% to 3% of gastrointestinal malignancies, and 0.4% of all malignancies. The annual incidence of small bowel cancer is about 5640 cases, with 1090 deaths related to small bowel cancer per year in the United States. Malignant lesions have a slight male predominance; benign tumors occur with roughly equal gender incidence. Over the last decade, the incidence of two small bowel tumors, lymphomas and GISTs, has increased substantially. In the case of primary small bowel lymphomas, incidence in the United States has nearly doubled in the last 2 decades, as a result of the increased numbers of immunocompromised patients (i.e., those with acquired immunodeficiency syndrome [AIDS] or rheumatoid arthritis, transplant recipients with immune disorders, or individuals with congenital immunodeficiency syndromes) and immigrants from third-world countries. In the case of GISTs, the application of KIT protein (CD117) immunohistochemistry has changed the way spindle cell tumors of the gastrointestinal tract are classified. Previously most intestinal sarcomas were considered to be leiomyosarcomas, but now it is clear that they are in fact GISTs. Because of this increased awareness and recognition, the annual incidence of new cases of GIST in the United States has greatly increased and is estimated to be as high as 4000. The stomach is the most frequent (60%) site of GIST, whereas approximately 30% occur in the small intestine.