Over 50% of American women suffered from dysmenorrhea and 10% of them will take sick leave for 1-2 days. Previous randomized control studies have demonstrated the pain relief effect of using high frequency TENS in dysmenorrheal pain. However, no investigation has been conducted to investigate the effect of high frequency TENS in female population in our country. The purpose of this study is to investigate the effect of high frequency TENS and compare to the placebo effect by sham TENS in a randomized control study.