OF ALL the duodenal tumors, the leiomyosarcomata are the rarest. After a thorough search of the literature, only 27 such tumors have been recorded, making the present case summary the 28th leiomyosarcoma of the duodenum to be published. However, it is not only the rarity of the disease that prompts the report of this additional case, but also the confused picture exhibited by the roentgenograms and the clinical symptoms. Von Salis,1 in 1920, was the first to report a case of leiomyosarcoma of the duodenum. All cases published since that time have been carefully reviewed and are cited in this paper, thus bringing the surgical literature up-to-date for this disease. Pathologists differ as to the origin of these tumors. Some believe that leiomyosarcomata are a transformation from the benign leiomyomata, while others maintain that they are malignant from the outset (Ewing). The tumor originates in the muscular layer of