Somatostatinomas are rare functioning neoplasms usually arising in the pancreas and duodenum. They are seldom associated with typical clinical symptoms. Their diagnosis is confirmed only by histological and immunohistochemical studies and the presence of specific hormones. Two distinct clinicopathological forms of somatostatinoma exist: duodenal and pancreatic somatostatinomas. Clinically, compared to pancreatic somatostatinomas, duodenal somatostatinomas are more often associated with nonspecific symptoms and neurofibromatosis, but less often with somatostatinoma syndrome or metastasis. We report a case of somatostatin-producing duodenal carcinoma in a 45-year-old female with neither neurofibromatosis nor somatostatinoma syndrome. Abdominal computed tomography showed a 18 mm mass in the duodenum which had given rise to multiple lymph node metastases. Although the endoscopic biopsies were free of malignancy, the patient subsequently underwent Whipple's operation for the duodenal mass. Immunohistochemical analysis confirmed the diagnosis of somatostatin-producing carcinoma.