Hypertension is not only a well-established cardiovascular risk factor but also increase the risk of atherosclerosis. Most studies conducted to investigate the effectiveness of treatment for cardiovascular disease such as hypertension have focused primarily on conventional drug and physiotherapeutic treatments. BanhabackchulChunma-tang(半夏白朮天麻湯:BCT) is popular herbal medicine used in clinic for the treatment of various symptoms of drulatory disorders and weakness of digestive system, including anorexa and nausea with vertigo, severe headache, vomiting and so on. However, the mechanisms underlying its efficacy are unknown. This study investigated the effects of BCT as an alternative medication on the contraction induced by phenylephrine and KCI in rat thoratic aorta. BCT revealed siginificant relaxation on phenylephrine-induced arterial contraction, but revealed noncompetitive effect on concentration responses of phenylephrine-induced contraction. Treatment of N-L^ω -argine methyl ester(L-NAME) and methylene blue(MB)(10^-5M) reduced the relaxation of BCT. BCT also increased in vitro NO production. It suggest that the relaxation effect of BBT is related with NO pathway, becausse the effect of L-NAME and MB are due to inhibition of NO synthesis from endothelial cells. These results indicate that BCT would be effective in hypertension treatment and its mechanism of relaxtion on arterial contraction is likely to be related with NO production, blocking of α-receptor and signal transduction after receptor activation.