The methanol extracts of 42 Korean indigenous plants were evaluated for the DNA strand-scission activity. As a result, the 17 extracts were found to be active in the criteria of $IC_{50}$}<$25;{mu}g/ml$. Among others, the MeOH extracts of Caesalpinia sappan and Mucuna birdwoodiana showed the most potent DNA strand-scission activity with $IC_{50}$ values of 5.9 and $4.9;{mu}g/ml$, respectively. Therefore, the partition and fractionation for C. sappan were performed and tested in the DNA strand-scission assay system for further bioassay-guided fractionation.