In the three and one-half year period from July 1, 1928, to Dec. 31, 1931, 4 cases of pylephlebitis were encountered at operation. Of this number, 3 were found as complications of 1,027 cases of acute appendicitis and 1 of 112 cases of acute cholecystitis. Although relatively uncommon, the dread results make this a formidable complication of acute intra-abdominal visceral disease. Pylephlebitis may be developed in three ways: (a) by direct introduction of organisms into the lumens of vessels emptying into the portal vein; (b) by continuity from continuous organs when pyogenic organisms pass through the vessels from without, causing first phlebitis and then thrombosis; (c) in infections of the blood stream in which collections of micro-organisms that pass through other capillaries may settle in the liver because of the retardation of the blood stream where they multiply and then reach the portal vein and cause thrombophlebitis. In this article