In patients with proven hyperinsulinism, localization of the underlying insulinoma may be difficult. The localization diagnosis may be performed preoperatively using different procedures, such as ultrasonography, computed tomography, selective arteriography of the pancreatic vessels and percutaneous transhepatic blood sampling in the portal venous system. At operation, insulinomas may be detected by inspection and bidigital palpation, pancreatico-sonography and rapid determination of insulin concentration after sampling of blood in pancreatic veins. By discussing the advantages and disadvantages of each localization procedure, the authors propose a strategy fort the detection of pancreatic insulinomas.