Simultaneous measurement of the hepatic artery and the portal vein was performed successfully upon 15 anesthetized patients during abdominal operations with the use of transit time ultrasonic volume flowmeter. The hepatic arterial flow, portal venous flow and total hepatic flow were 267.3 +/- 21.2, 746.4 +/- 41.3 and 1,010.7 +/- 52.7 milliliters per minute, respectively. The ratio of hepatic arterial flow to portal venous flow was 0.36 +/- 0.03. Temporary occlusion of the portal vein resulted in a significant increase in hepatic arterial flow (23.6 +/- 4.3 per cent, p less than 0.01), whereas temporary occlusion of the hepatic artery did not alter portal venous flow significantly. Occlusion of the common hepatic artery induced a significant decrease in hepatic arterial flow (p less than 0.05), but did not alter portal venous flow significantly. The results of this approach had useful clinical meanings in one patient in whom the Appleby's operation was performed in which sufficient hepatic arterial flow was needed after the common hepatic artery was ligated. Data are presented for hepatic circulation measured by transit time ultrasonic volume flowmeter, which is a good device to use to assess portal venous flow as well as hepatic arterial flow with reproducibility and stability.