Smooth muscle tumors of the alimentary tract are uncommon. A retrospective study was made of 7 patients treated for leiomyosarcoma of the small and large bowel to identify prognostic factors that influence results. The symptoms associated with these tumors varied according to the anatomic sites of the lesions and the position of the growth in relation to the intestinal lumen but the most common presenting clinical signs are bleeding or obstruction. The differential diagnosis between benign and malignant smooth muscle tumors is sometimes quite difficult. Clinical behavior of the myosarcomas of the gastrointestinal tract can be predicted to a large extent by the site of the tumor, the presence or absence of invasion of adjacent vital organs, and the histopathologic grade of malignancy. Although the mitotic activity of a gastrointestinal stromal tumor remains the most critical prognostic factor, tumors have been seen to recur locally and to metastasize even with rare or absent mitotic figures. Further studies are needed to pinpoint the factors that may be correlated to the prognosis.