Despite the fact that as much as 25 percent of the total cardiac output goes to the splanchnic vascular bed, only meager information is available relating to the hemodynamic changes that occur in this circulation during normal and abnormal conditions. With a new experimental model that has been developed in this laboratory, we will measure simultaneously blood flow in the superior mesenteric artery, hepatic artery, and portal vein in the unanesthetized dog. Electromagnetic flow probes will be used for these determinations. It is planned to study the hemodynamic characteristics of splanchnic flow under varying conditions such as, alimentation, cardiogenic shock, hemorrhagic shock, and pharmacologic manipulation with vasoactive drugs. In addition, the characteristics of blood flow distribution within the liver and gut will be studied by means of radioactive tracer techniques. This study is designed to provide a better understanding of those mechanisms that control the splanchnic circulation during normal and abnormal hemodynamic conditions.