The methanol and benzene extracts of the leaves of 55 higher plants in Korea were tested for their antibacterial activity against three Gram positive bacteria, Streptococcus mutans, Staphylococcus aureus and Bacillus subtilis, and one Gram negative bacterium Escherichia coli. Among them, the methanol extract of the leaves of Liriodendron tulipifera showed remarkably potent antibacterial activity against both Gram positive and negative bacteria.