Abstract Lymphosarcoma may involve any portion of the intestine but has a predilection for the ileum. In the colon its most common location is in the rectum. The condition is rare, about three hundred cases having been reported. The growth of the tumor is extremely rapid and the condition may terminate fatally in a few weeks or months. There is nothing characteristic about the symptomatology and the disease is rarely recognized before operation or necropsy. Roentgenologic examination may be of considerable help in locating the lesion in some cases and offering a clue as to its identity. The prognosis is bad, and either eradication or some form of sidetracking operation is the usual surgical procedure. A case of seven weeks' duration in a man, age twenty-three, is described. The early clinical picture was similar to that of acute gastritis. Nausea, weakness and loss of weight were the most important symptoms. Intestinal obstruction developed, and combined roentgenologic and fluoroscopic examination showed the seat of obstruction to be in the sigmoid. Cecostomy and delivery of the sigmoid growth through the left abdominal wall were performed but the patient died of peritonitis. Postmortem examination revealed a lymphosarcoma of the sigmoid with involvement of the abdominal lymph nodes. My thanks are due to Dr. Dalldorf, of the New York Hospital, for his cooperation, particularly with reference to the study of the postmortem findings.