The incidence of gastric adenocarcinoma has decreased in the United States over the past 70 years although it continues to have a poor prognosis. While radical resection was initially the primary treatment for adenocarcinoma of the stomach, systemic chemotherapy and radiation have been shown to play a role in prolonging survival in most patient populations. This chapter explores the evidence that guides treatment for gastric cancer today. It also discusses the treatment for gastrointestinal stromal tumors (GIST), and small bowel tumors. In addition to systemic therapies, this chapter explores the surgical management of gastric and small bowel tumors including the extent of the gastric lymph node dissection.