Horseradish peroxidase (HRP) is covalently immobilized on a self-assembled monolayer of mercaptopropionic acid on vapor-deposited gold electrode. The electrode allows the polyphenol detection down to 2 mu mol dm(-3) with a linear relationship up to 25 mu mol dm(-3). The reduction current of oxidized polyphenol intermediate formed during the enzymatic reaction in the presence of H2O2 is proportional to the concentration of polyphenol. The present method is applicable to the determination of the total polyphenol content in wine and tea.