Aims: To search for antimicrobial compounds against pathogenic bacteria from grape vines (Vitis spp.). To investigate the antimicrobial efficacy of active compounds towards methicillin-resistant Staphylococcus aureus (MRSA). Methods and Results: The root extracts of taiwanese wild grape (Vitis thunbergii var. taiwaniana) showed marked activities against Gram-positive bacteria using the disc diffusion method. After purification, the active compound 1 was confirmed as heyneanol A by mass spectroscopy and nuclear magnetic resonance. Heyneanol A showed an minimum inhibitory concentration (MIC) value of 2 mu g ml(-1) towards MRSA and a value of 2 to 4 mu g ml(-1) for Enterococcus faecium, S. aureus, Streptococcus agalactiae and Streptococcus pyogenes. In addition, the contents of heyneanol A were determined as 36 mg g(-1) in roots of taiwanese wild grape. Conclusions: The root extracts of grapevines have good antimicrobial activities towards some strains of Gram-positive pathogens. Heyneanol A, the major antimicrobial compound, is especially active towards MRSA. In addition, the abundances of heyneanol A and other stilbenes in the roots of grapevines make it possible to produce natural antimicrobial compounds from this plant species. Significance and Impact of the Study: This study reports for the first time the antimicrobial compounds in the root extracts of grapevines. The results will have clinical significance owing to their activities against MRSA.