Gastrinomas are rare neuroendocrine tumors (NETs) usually located in the duodenum or pancreas. Gastrinomas secrete gastrin and cause a clinical syndrome known as Zollinger-Ellison syndrome (ZES), which is characterized by gastric acid hypersecretion resulting in severe acid-related peptic disease (peptic ulcer disease, gastroesophageal reflux disease), and diarrhea. Gastrinomas can be either nonhereditary (sporadic) or hereditary, which are associated with multiple endocrine neoplasia type 1 (MEN-1) syndrome. In this chapter, we review the clinical symptoms, diagnosis, differential diagnosis, and management of gastrinomas. The focus is on the evidence of surgical treatment, on the surgical choice and procedure for sporadic gastrinoma, gastrinoma with MEN-1 without hepatic metastases, gastrinoma with hepatic metastases, recurrent gastrinomas, and gastric hypersecretion. © 2015 by John Wiley & Sons, Ltd. All rights reserved.