Approximately half of pancreatic neuroendocrine tumors (PNETs) are nonfunctioning, and insulinoma and gastrinoma are frequent forms of functioning tumors. The treatment of patients with PNETs should be based on the consideration that more than half are malignant except for insulinomas. Multiple endocrine neoplasia type 1 (MEN1) is often complicated with gastrinoma. Endoscopic ultrasound and somatostain receptor scintigraphy are useful in diagnosing PNETs, and the selective arterial secretagogue injection test is performed if necessary. WHO2010 is available as a histopathologic grading system of malignancy. Although surgical resection should first be considered as a treatment for PNETs, liver metastasis is a major factor hindering resection. In Japan, the choices of drugs to treat liver metastases are too few. In patients with MEN1 in whom PNETS are frequently multiple, we should perform procedures that preserve pancreatic function, although some patients may require total pancreatectomy for the complete resection of tumors. The indications for total pancreatectomy should be determined individually based on the tumor status and patient age.