In order to prevent excessive blood loss during liver surgery, an intermittent Pringle manoeuvre (IPM) can be applied. This implies a temporary clamping of the portal vein and hepatic artery in the hepatoduodenal ligament in order to occlude hepatic inflow. The optimal duration of the IPM is unknown. This randomized controlled trial aimed to analyse differences in hepatocellular damage after 15 minutes or 30 minutes IPM during liver surgery for primary or secondary liver tumours.