The hepatic arterial buffer response (HABR) is an intrinsic regulatory mechanism of the hepatic artery (HA) that compensates for reductions in portal venous (PV) blood flow. Whether this response is maintained in patients with cirrhosis (LC) is unclear. The aim of the present study was to examine whether HABR is maintained in patients with LC using direct blood flow measurements. PV and HA blood flow were intraoperatively measured and compared in patients with (LC group, n = 39) or without (control group, n = 22) cirrhosis at baseline (baseline HABR) and after PV clamping (acute HABR) using an ultrasound transit-time flowmeter. In contrast to the proportional relationship between the baseline PV and HA blood flow observed in the control group, HA blood flow and the HA-PV flow ratio increased when PV blood flow decreased in the LC group, suggesting that the baseline HABR had already been activated. Acute HABR, evaluated by the absolute and relative changes in HA blood flow and by the buffer capacity, was blunted in the LC group (P < 0.001, P < 0.01, and P = 0.01, respectively). An association between the degree of acute HABR impairment and the level of baseline HABR activation (HA-PV flow ratio) could not be confirmed in the LC group. In conclusion, the baseline HABR appears to be continuously activated in patients with LC; this phenomenon probably results in the impairment of the acute HABR. (Liver Transpl 2005;11:684–691.)