Thermogenesis in the viscera (liver and intestines) was studied in normal, artificially cooled and heated animals, as well as during febrile states caused by homogeneous and heterogeneous blood transfusions. The expts. were made on angiostomized dogs with cannulas in the portal and hepatic veins; in each animal the rectal temp. and the temp. of the blood in the abdominal aorta and the portal and hepatic veins were measured. The thermoelectric method used throughout the expts. detected changes in temp. with sufficient accuracy and made it possible to study thermotopography in the organism. In normal fasting dogs the lowest temp. of the blood was found in the aorta and the highest in the hepatic vein. The expts. showed important thermogenesis in the intestines. When the animals were cooled by the application of ice to the skin, the difference in temp. between the blood in the hepatic and the portal veins increases, i.e., there was a rise in hepatic heat production (3 to 6 times the original level), providing the blood flow was accelerated; when the animal was overheated, the reverse took place. Homogeneous blood transfusion did not bring about noticeable changes in thermogenesis in the liver and the intestines, despite a systemic rise in temp. The febrile state caused by heterogeneous transfusion is accompanied by a noticeable increase in thermogenesis in the liver and intestines. A comparative study of the hemodynamic variations has shown that the increase in hepatic and intestinal thermogenesis cannot be explained by the influence of circulatory factors. After anaphylactic shock, the same changes were observed as in the case of heterogeneous transfusion, but the variations in temp. were much greater, especially with respect to the intestines. The increase in visceral thermogenesis proceeds parallel to the systemic temp. reaction, i.e., the liver and the intestines participate in determining the febrile process accompanying the transfusion of foreign blood. The use of the method of E. I. London for studying visceral thermogenesis in angiostomized dogs considerably widens the sphere of its application and promises to give results of great practical and theoretical interest.