In normotensive rats, equol displayed vasorelaxant activity similar to daidzein. The relaxant effect of equol was independent of intact endothelium, NOS activity, K+ channels, and gender. In the basilar artery, where superoxide levels are higher, equol exerted weak antioxidant effects, whereas the effects of daidzein were insignificant. During hypertension, equol-induced vasorelaxation was preserved, whereas relaxant responses to daidzein were impaired. The gene discussed is NOS2; the disease is Hypertension.