Arbutus unedo leaf is used traditionally for gastrointestinal complaints. Ethanol extracts from Arbutus unedo collected in both Montenegro (AuM) and Greece (AuG) were found to decrease the ileal basal tonus, with AuG producing a significantly higher (p < 0.05) reduction in contractile response to acetylcholine. AuM and AuG relaxed 80 mM K(+) induced contractions and shifted the Ca(++) concentration-response curves to the right, similar to that caused by verapamil, suggesting that the spasmolytic effect was induced through calcium channel inhibition. The antioxidant activity of AuM and AuG and the phenolic content of the extracts and dry plant material were studied, and both extracts were found to possess considerable antioxidant properties. AuG showed a stronger in vitro antioxidative activity in the DPPH assay and in the TBA test. Polyphenol, tannin and flavonoid levels were higher in AuG, supporting the more potent spasmolytic and antioxidative effects, whereas the arbutin content was higher in dry plant material collected in Montenegro.