The purpose of this study was to demonstrate that galactose clearance (GC) can measure acute changes in liver blood flow (LBF) in normal and cirrhotic dogs. Ten dogs were studied. GC was measured preop. At laparotomy, GC, hepatic artery (HA) flow, portal vein (PV) flow, and cardiac output (CO) were measured at baseline, 50% portal vein occlusion (PVO), and portal vein release. HA and PV flows were measured using a flow probe (FP). Common bile duct ligation was then performed to cause cirrhosis and all measurements were repeated in 7 weeks. Statistical analyses showed that on PVO in both normal dogs (n = 10) and cirrhotic dogs (n = 5) the GC, HA flow, and CO were significantly different from their baseline values. In both groups PVO caused HA flow to increase, thus keeping FP-LBF unchanged while GC-LBF was significantly reduced compared to baseline. The possible explanations for this are discussed in the text. PVO also caused a significant reduction in CO due to splanchnic pooling in both normal and cirrhotic dogs. In both groups PVO results in an increased percentage of CO going to FP-LBF, while the percentage of CO going to GC-LBF remains unchanged. We conclude that GC can measure acute changes in LBF caused by a 50% PVO in both normal and cirrhotic dogs.