BACKGROUND: Hemodilution reduces the concentration of clotting factors in blood and this may induce some degree of impairment of coagulation. But there are some evidence that hemodilution may induce a hypercoagulable state. The goal of this study is to investigate the changes of coagulation status during progressive hemodilution. METHODS: Whole Blood was diluted by 10% increment to 80% with 0.9% normal saline. At each 10% dilution blood coagulation status was analysed using thrombelastography (TEG) and was compared with that of an undiluted control specimen obtained concurrently from the same patients. RESULTS: Hemodilutions up to 40% decrease r and K times and increase values of MA and angle. Hemodilutions more than 70% increase r and K times and decrease values of MA and angle. CONCLUSIONS: Hemodilutions up to 40% increase coagulability and hemodilutions more than 70% decrease coagulability of whole blood in vitro.