The duodenum is the seat of tumors of mesoblastic origin in rare instances. Leiomyosarcoma of the duodenum is of interest because of its extreme rarity and because of its similar behavior in every case reported, as will be shown. Only five cases have been reported to date. We record the sixth case and give a brief review of the literature. Our search reveals only three articles that are confined to the subject of leiomyosarcoma of the duodenum. The articles are in the main case reports. A comparative study of these cases has not been made heretofore. Perhaps this is because the series is so small. In this paper we shall not attempt to discuss leiomyosarcoma of the gastrointestinal tract except as it pertains to cases involving the duodenum. Raiford,1 in his treatise on tumors of the small intestine, has dealt with the subject in such a thorough fashion that