Purpose: This study was to examine the effects of magnetic therapy applying the principal of Sa-am Acupuncture on menstrual cramps and dysmenorrhea in high school students. Methods: A quasi-experimental nonequivalent control group, pre- and post-test design was used. Participants were 60 female high school students living in S city, 30 in the experimental group and 30 in the control group. Data were collected from February to August 2008. Magnetic therapy was performed three days before menstruation for three menstrual cycles. Results: Magnetic therapy significantly reduced menstrual cramps and dysmenorrhea. There was a significant difference in menstrual cramps and dysmenorrhea between the experimental and control groups. Conclusion: Magnetic therapy may be an effective nursing intervention in reducing menstrual cramps and dysmenorrhea.