As part of our screening of anticariogenic agents from medicinal plants, the ethanol extracts of 25 herbs widely used in the fork medicine were tested for the antimicrobial activity against a cariogenic bacterium Streptococcus mutans ATCC 25175. The ethanol extracts of Coptis chinensis, Sophora flavescens, Glycyrrhiza uralensis, Mentha arvensis, and Saururus chinensis showed antimicrobial activities against S. mutans. The extracts of Coptis chinensis and Sophora flavescens among these medicinal plants showed significant antomicrobial activity against S. mutans. These results suggested that the extracts of Coptis chinensis and Sophora flavescens could be the potential source of antimicrobial agent against S. mutans ATCC 25175.