Leiomyosarcoma of small intestine is an uncommon tumor, comprising less than 20 percent of all primary malignant tumors of small intestine. Duodenal leiomyosarcoma is rare disease which amount to about 20 percent of all small bowel malignancy but potentially curable tumors often diagnosed at an advanced age, so its five-year survival following resection approximates 50% in reported series. Recently, several cases of leiomyosarcomas of duodenum were diagnosed by hypotonic duodenograhy in Korea. We experienced a woman with duodenal leiomyosarcoma that was diagnosed by endoscopic duodenal biopsy and received currative resection of the tumor(Whipple's operation). We report the case with review of the literatures.