BACKGROUND: Individuals with type O blood are more likely to have reduced factor VIII and von Willebrand factor levels compared to their non-O counterparts. Hydroxyethyl starch (HES), which is widely used for blood volume replacement, can induce coagulopathy. Therefore, we tested whether blood type O patients show more coagulopathy and blood loss than non-O patients after infusion of 6% HES. METHODS: Thirty-four non-O and 20 type O patients scheduled for posterior lumbar interbody fusion (PLIF) involving 3 vertebrae or less from June 2007 to August 2008 were enrolled. Fifteen ml/kg of 6% HES was administered during the operation. Coagulation profiles was checked at pre-infusion (T0), 5 min after the end of infusion (T1), 3 hr after the end of infusion (T2), and 24 hr after the end of infusion (T3). Bleeding was measured during and after surgery for 24 hours. RESULTS: Baseline factor VIII concentration was lower and aPTT was longer in type O patients compared to those of non-O patients. 6% HES infusion decreased most of the coagulation factors at T1 in both groups, which were recovered in a time dependent manner. Factor VIII and aPTT of blood type O patients fell off the normal range at T1. However, other coagulation factors, thromboelastography variables, and blood loss were not different between the groups. CONCLUSIONS: Despite inborn low factor VIII which further decreased shortly after HES infusion, blood type O patients did not show more blood loss than non-O blood type after 15 ml/kg of HES infusion in PLIF surgery.