In our previous study, Welsh onion (Allium fistulosum L., Alliaceae), an important flavoring vegetable in Asian dishes, has been shown the effect of lowering blood pressure, modulating aortic vascular tone and inhibiting platelet aggregation. There is no previous report concerning if Welsh onion can modulate antioxidant enzyme activities or GSH level. In this study, spontaneously hypertensive (SHR) and normotensive (WKY) rats were fed with Welsh onion extract for 28 days, and the body weight, blood pressure, the level of hepatic oxidative damage and antioxidant enzyme activities were compared between the fed and control animals. Our results showed that (1) lipid peroxidation was decreased in both SHR and WKY rats (19% and 25%, respectively). (2) The amount of GSH is not significantly changed in SHR but is increased 34% in WKY rats.