Ferulic acid (4-hydroxy-3-methoxycinnamic acid) is a phenolic compound contained in rice bran and other plants. The effect of ferulic acid on blood pressure (BP) was investigated in spontaneously hypertensive rats (SHR). After oral administration of ferulic acid (1 to 100 mg/kg) to SHR, systolic blood pressure (SBP) significantly decreased in a dose-dependent manner. When oral ferulic acid (50 mg/kg) was administered to SHR, BP was lowest at 1 h and returned to basal levels at 6 h. There was a significant correlation between SHR plasma ferulic acid and changes in the SBP of the tail artery, suggesting that absorbed ferulic acid reduces BP. When 7-week-old SHR were given 10 and 50 mg/kg/d of ferulic acid for 6 weeks, increases in BP were significantly attenuated compared to SHR on the control diet. Intravenous injection of ferulic acid dose dependently reduced carotid arterial pressure in anesthetized SHR. Furthermore, the depressor effect of intravenous ferulic acid (1 mg/kg) was significantly attenuated by pretreatment of SHR with the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 3 mg/kg, administered intravenously). These data suggest that the hypotensive effect of ferulic acid in SHR is associated with NO-mediated vasodilation.