Objectives: Volume replacement using hydroxyethyl starch (HES) 130/0.4 impairs blood coagulation less than HES 200/0.5. We hypothesized that HES 130/0.4 may be used at higher doses without increasing the risk of perioperative bleeding and transfusion requirements. Methods: We randomized 120 patients scheduled for elective CABG to receive either up to 50ml/kg of 6% HES 130/0.4 or up to 33ml/kg of 6% HES 200/0.5 for volume replacement during surgery and until 24h thereafter. The first 33ml/kg of HES in both groups were administered in a double blind fashion. Volume requirements in excess of the respective maximum dose of HES were covered with gelatin. Colloid use was at the discretion of the attending physicians and not dictated by protocol. Results: The median volumes of HES administered were 49ml/kg and 33ml/kg in the HES 130/0.4 and HES 200/0.5 groups, respectively (p<0.001). Consequently, patients in the HES 130/0.4 group required less gelatin in addition to HES than those in the HES 200/0.5 group (7 vs. 20ml/kg [medians]; p<0.001). The combined volumes of HES and gelatin were similar for both groups (p=0.21). The 24-h chest tube drainage as well as erythrocyte transfusions were similar for both groups. Ten HES 130/0.4 patients and 19 HES 200/0.5 patients received a median of 2 FFP units (p=0.054). Conclusions: High-dose 6% HES 130/0.4 at a median dose of 49ml/kg did neither increase blood loss nor transfusions compared with 6% HES 200/0.5 at the manufacturer's recommended dose of 33ml/kg.