BACKGROUND: Acute isovolemic hemodilution is one of the autologous transfusion which diminishes intraoperative blood loss and avoids homologous transfusion. A method of assessment of hemostatic function by whole blood is thrombelastography, which is a sensitive indicator of platelet interreaction with protein coagulation cascade. We investigated the effect of intraoperative isovolemic hemodilution on blood coagulation as measured by thrombelastography. METHODS: We studied in twenty-one patients undergoing elective total hip replacement arthroplasty. Hemodilution was done with Hartmann's solution and pentastarch and prothrombin time, activated partial thromboplastin time and native whole blood thrombelastography were performed preoperatively, immediate postoperative and days 2 postoperatively. RESULTS: The Hb, Hct and platelet count decreased significantly after hemodilution. The thrombelastographic changes included decreases in r and k with concurrent increases in alpha angle and MA in immediate postoperative time. On days 2, there were further increase in alpha angle and MA. These changes indicate enhanced procoagulant activity and progressive increase in maximum clot strength. Conclusion: Acute isovolemic hemodilution with Hartmann's solution and pentastarch induced hypercoagulable state without any serious complication in total hip replacement arthroplastic surgery.