BACKGROUND: As the menstruation has been thought to be associated with abnormal hemostasis and increased fibrinolytic activities, some surgeons and even anesthesiologists tend to postpone elective surgery. Many investigators have studied individual coagulation profiles and fibrinolytic activity during the menstruation, but conventional coagulation screens are frequently inadequate for the purpose of monitoring coagulation dynamically. This study was designed to evaluate the whole dynamic hemostatic process globally during the normal menstrual cycle by the thromboelastography (TEG). METHODS: Thirty six-healthy, normally menstruating female volunteers wrote a menstruation diary about their menstruation cycle. Blood samples were obtained for TEG analysis 3 days before menstruation, the 1st day of menstruation, the 2nd day of menstruation, the last day of menstruation and 5 days after menstruation. TEG coagulation indices (R value, K value, alpha angle, MA value and WBCLI60) were measured and statistically analysed with repeat-measured one way ANOVA. RESULTS: There were no significant difference in R value, K value, alpha angle, WBCLI60 during menstruation compared with pre- or post-menstruation period, but there was a significant decrease in the MA value on the 1st day of the menstruation. CONCLUSIONS: The result of our study showed the possibility of abnormal hemostatic function on the 1st day of menstruation. However, the more study is needed to confirm the possibility of bleeding tendency during surgery on the 1st day of menstruation.