Primary tumors originating in the mesentery are relatively uncommon but have received considerable attention in the surgical literature. They have been divided into two main groups, cystic and solid. Of these, the former are more prevalent according to most authors, although Rankin and Major (14) have reported a series of 22 cases of mesenteric tumors from the files of the Mayo Clinic with solid tumors outnumbering the cystic form 15 to 7. There have been numerous discussions as to the exact definition of a mesenteric tumor. Some authors consider any neoplasm which extends into the mesenteric tissues, regardless of its point of origin, to represent a tumor of the mesentery ; others limit the term to those primary growths which have their origin in the connective tissue between the leaves of any of the peritoneal folds, omenta, or mesenteries. Lipomatous tumors which fulfill the requirements of this more exact definition are rare, although lipomata are the most frequent benign solid type of mesenteric tumor, accounting for 33 per cent of the 15 solid tumors in the series of Rankin and Major and 27 per cent of the 56 cases reviewed by Harris and Herzog (7). For more detailed discussion of the classification, as well as the etiologic theories, of mesenteric tumors, reference may be made to the articles by the abovementioned authors and to the publications of Carter (4), Judd and McVay (8), and Phillips (13). Mesenteric lipomata may reach large proportions before symptoms are produced. Bergouignan (2) reported one which weighed over 8 kilograms, and Lambrecht (10) described a case in which a tumor weighing 7.5 kilograms was removed. These fatty tumors are frequently multiple, and they show a marked tendency to local recurrence. Some authors (12) have observed that up to one-third of the cases of abdominal lipomata may show sarcomatous changes. The treatment is surgical removal whenever possible. The symptoms of these fatty tumors are quite variable, depending upon their size and position, as well as upon the rapidity of growth. One patient was known to have had a large palpable mesenteric lipoma for eighteen years, but the usual history is much shorter. If the tumor is located close to the bowel, symptoms of obstruction may occur. The mass may be so situated as to produce urinary symptoms; and torsion of the bowel, with its resultant symptomatology, has also been noted. Often the chief complaint is a minor one, and some patients seek medical attention because of the discovery of a painless mass in the abdomen. The physical findings in these cases likewise show considerable variation. A palpable abdominal mass with some degree of mobility, often to the right and below the umbilicus, should cause mesenteric tumor to be included in the differential diagnosis, although it is not the most common cause of such a mass.