Estrogen stimulates endothelial nitric oxide (NO) production and attenuates endothelial dysfunction in ischemia/repurfusion and menopause. Recent studies have shown that phytoestrogens from dietary sources improve endothelial function and reduce cardiovascular risks. The Thai medicinal plant Pueraria mirifica (PM) contains many potent phytoestrogens including miroestrol and deoxymiroestrol but no study on vascular function has been established. Ground powder of PM was orally given to ovariectomized White New Zealand rabbits (OVX + PM group) (n = 4) weighing 3.2-4.0 kg at the dose of 100 mg/kg for 90 days. Saline-treated ovariectomized rabbits were assigned as a control group (OVX group) (n = 5). At the end of treatment thoracic aorta was isolated for functional evaluation. Maximal relaxant response to acetylcholine (ACh) was significantly increased (24%) with 3.5-fold decrease in EC50 while no change in relaxant response to sodium nitroprusside was observed Minimal and maximal responses to 17beta-estradiol (E2) were increased in the OVX + PM group and L-NAME (100 mM) attenuated Emax of E2. PM significantly decreased maximal contractile responses to norepinephrine (NE), but no change in EC50 was observed. In addition to vascular study, the authors found no significant alteration in serum cholesterol, LDL, triglyceride, HDL, ALT AST alkaline phosphatase, and lipid peroxidation in OVX + PM rabbits. These data demonstrate that PM (100 mg/kg/d) improved endothelial function through NO-dependent pathway and increased response to E2 while sensitivity to NE was reduced. In addition, it had no impact on lipid profile, liver enzymes, and ALP activities. PM is a potential source of phytoestrogens for postmenopausal women to improve cardiovascular function or reduce cardiovascular risks.