The present study examined the effect of the methanol extract of lsaria sinclairii, a kind of Donchunghacho (Tochukaso), on blood pressure in spontaneously hypertensive rats (SHR). Blood pressure and heart rate were measured after treatment with the methanol extract of l. sinclairii by the indirect tail-cuff method and the direct in vivo model. Starting at 12 weeks of age, male SHR were treated with the extracts for 2 or 4 weeks. We found that, when compared to untreated control SHR, oral treatment with l. sinclairii methanol extract (30 mg/kg/day) remarkably decreased systoiic blood pressure from 200 to 112 mmHg and decreased diastolic blood pressure from 114 to 88mmHg. Furthermore, efficacy of methanol extract of l. sinclairii was superior to captopril (30mg/kg/ml, positive control), an angiotensin-converting enzyme inhibitor, with a lowering effect that dropped systolic blood pressure from 201 to 130 mmHg and diastolic blood pressure from 102 to 92 mmHg. However, in normal Wistar Kyoto rats, l. sinclairii methanol extract did not significantly change the normal blood pressure, suggesting that this type of Dongchunghacho has a selective effect against hypertension. Therefore, methanol extract of l. sinclairii may be used as an anti-hypertensive food/agent. Furthermore, this extract also has multiple actions such as No production in endothelial cells, inhibiting thrombininduced blood coagulation by thrombin and mildly decreasing in prostaglandin E$_2$ levels in cultured macrophage cells, all of which might contribute to protection against atherogenesis and thrombus formation. HPLC and MS analysis of methanol extract of l. sinclairii revealed the presence of adenosine.