Primary duodenal carcinoid causing a malignant carcinoid syndrome is rare. Herein a case is reported. In view of this case and a review of the literature, the carcinoid syndrome is almost pathognomonic of massive liver metastasis or involvement of organs whose venous drainage is not through the portal system. The right upper quadrant abdominal pains accompanied by symptoms that resemble even part of the carcinoid syndrome should initiate the investigational process including proximal gastrointestinal endoscopy to avoid delay in diagnosis of duodenal carcinoid.