Using an ultrasonic Doppler duplex system, we investigated the portal hemodynamics of two patients with portal thrombosis after splenectomy and esophageal transection for portal hypertension accompanied by liver cirrhosis. In both cases, the preoperative blood flow volumes of the splenic and portal veins were especially high, but were markedly lower--even than normal--after the operation. However, the results of pre- and postoperative peripheral platelet counts and coagulation function tests did not differ remarkably. The dramatic change in portal hemodynamics caused by the splenectomy was thought to be the main factor in the formation of the portal thrombi.