It has been questioned whether the Pringle maneuver induces complete ischemia of the liver. We examined changes in liver blood flow (LBF) in sixty patients who underwent liver resection, under conditions of prolonged inflow occlusion. The ischemia period ranged from 30 to 75 minutes. All patients tolerated the procedure. To better understand the metabolic consequences of ischemia, 10 female mongrel pigs were divided into two groups treated with hepatic inflow occlusion or total vascular exclusion for one hour (n = 5, each). Clinical and experimental data showed approximately 10% of residual LBF under the Pringle maneuver. Only one out of five animals tolerated complete ischemia (total vascular exclusion) in terms of 7-day survival while all pigs treated with the Pringle method survived. This was attributed to the lower serum transaminase levels and attenuation of liver adenosine triphosphate (ATP) decline in the inflow-occluded group. Our data indicate that the Pringle maneuver induces partial rather than full ischemia of the liver and hepatic vein "back flow" is likely to be the cause. The clinical implications of hepatic inflow occlusion for liver surgery are discussed.