A number of investigators have been interested in the circulatory response consequent to total occlusion of the thoracic aorta1,2,5,13,19,30,32and the inferior vena cava,7,8,14,17as well as the effect of occluding both sites simultaneously.8,10Despite the prominent role of the splanchnic circulation as it determines or reflects changes in the over-all metabolic and hemodynamic schema, few papers2,8,14have dealt with the effect of these obstructions on the blood flow to this region. However, the splanchnic response to other alterations in the circulation has received a great deal of attention.9,12,22,24,34 The purpose of this investigation was to study the splanchnic response to the simultaneous occlusion of the thoracic aorta and the abdominal vena cava as it is related to the over-all response, with an emphasis on the metabolic changes consequent to the altered circulation. Materials and Methods Sixteen adult mongrel dogs ranging in weight from 13