A fifty-six year-old woman visited our institute, suffering from lower abdominal pain. A tumor was palpable in the pelvic cavity, having the diameter of 9.7 cm, as measured by transvaginal ultrasonography (US). Computed tomography and magnetic resonance imaging (MRI) revealed a high contrast-enhancement and the central necrosis of the tumor. Surgical resection was performed, and the tumor was found to have originated in the duodenum. Immunohistochemistry confirmed positive KIT, and the mitotic index was 4 per 50 high power field, so that the final diagnosis was a gastrointestinal stromal tumor of intermediate risk. After two years of observation, multiple liver metastases were found. Hepatectomy was performed as a volume reduction surgery, leaving three small lesions in the remnant liver. Imatinib administration was initiated at 400 mg a day two weeks after the surgery, but was interrupted two weeks later because of severe anorexia and a body weight gain of 7 kg due to the increased ascites and edema. Imatinib was resumed at 200 mg/day after a one-month interval. She has been enjoying relapse-free survival for 8 years since the recurrence was diagnosed. Although neither reduction surgery nor dose reduction of imatinib below 300 mg/day is recommended, there may be a possibility that a smaller tumor might be controlled by a lower dose of imatinib.