Intraductal papillary mucinous neoplasm (IPMN) is characterized by cystic dilatation of the main and/or branch pancreatic duct. Only one-third of all patients are symptomatic, and others are diagnosed by chance. IPMNs are classified into 3 types: main duct, branch duct, and mixed IPMN. Most branch-type IPMNs are benign, while the other 2 types are frequently malignant. The presence of large mural nodules increases the possibility of malignancy in all types. Presence of a large branch-type IPMN and marked dilatation of the main duct indicate, at the very least, the existence of adenoma. Ultrasonography, endosonography, and intraductal ultrasonography clearly demonstrate ductal dilatation and mural nodules, and magnetic resonance pancreatography best visualizes the entire outline of IPMN. Not infrequently, synchronous or metachronous malignancy develops in various organs, including the pancreas. Prognosis is excellent after complete resection of benign and noninvasive malignant IPMNs. Asymptomatic branch-type IPMNs without mural nodules may be followed up without resection. Malignant IPMNs displaying acquired aggressiveness after parenchymal invasion require adequate lymph node dissection. Total pancreatectomy is needed for some IPMNs; its benefits, however, must be balanced against operative and postoperative risks because most IPMNs are slow growing and affect elderly people, and prognosis is favorable for IPMN patients with even malignant neoplasms.