A 49-year-old man underwent partial resection of the jejunum for an abdominal tumor, which was histologically confirmed to be a gastrointestinal stromal tumor (GIST). Immunohistochemistry revealed that the tumor cells were positive for c-kit, p52, and MIB-1. He underwent resection of a total of 83 recurrent tumors over the next 36 months. A computed tomography (CT) scan done a few months later showed multiple tumor recurrences. The patient was started on imatinib mesylate 400 mg/day, and 3 months later, a CT image showed an increase in tumor size but a decrease in tumor density. Subsequent CT scans showed a marked decrease in tumor size 3 months later and no evidence of tumor recurrence 9 and 12 months after the commencement of imatinib treatment. The patient remains in complete remission 31 months after the start of treatment.