<jats:title>Abstract</jats:title><jats:p>This study examined the vascular effect of <jats:italic>Arbutus</jats:italic> leaves (aqueous extract) and described the isolation of several fractions responsible for their vasorelaxant activity. The aqueous extract (AE) of leaves was tested on rat aortic rings precontracted with 0.1 µ<jats:sc>m</jats:sc> noradrenaline. At 10<jats:sup>−2</jats:sup> g/L, AE produced an endothelium dependent relaxation of 66% ± 5%, (<jats:italic>n</jats:italic> = 8). The leaves of <jats:italic>Arbutus</jats:italic> were then extracted successively with different solvents and the methanol extract was the most active. When tannins (primarily condensed tannins) were precipitated from the methanol extract, they showed a strong vasorelaxant activity (87% ± 4%, <jats:italic>n</jats:italic> = 5), whereas the elimination of tannins in the methanol extract reduced significantly its vasorelaxant activity (42% ± 8%, <jats:italic>n</jats:italic> = 8, <jats:italic>p</jats:italic> < 0.005). The methanol extract was further separated semi‐preparatively by reversed‐phase HPLC. Four fractions (Fr2, Fr3, Fr4 and Fr6) were the most active and produced 88% ± 2% (<jats:italic>n</jats:italic> = 5), 75% ± 6% (<jats:italic>n</jats:italic> = 5), 76% ± 3% (<jats:italic>n</jats:italic> = 7) and 77% ± 3% (<jats:italic>n</jats:italic> = 10) relaxation, respectively. These four fractions mainly correspond to polyphenol compounds. Analysis of Fr6 indicated that this fraction contained catechin gallate. In conclusion, the vasorelaxant activity of <jats:italic>Arbutus</jats:italic> is likely to be due to polyphenol compounds, primarily condensed tannins and catechin gallate. Copyright © 2004 John Wiley & Sons, Ltd.