Objective : Kumsoouyukkun-joen extract(KSE) has been used treating asthma for a long time in korea. In the present study, I examined the effects of KSE on the ovalbumin(OVA)-induced airway hyper-reactivity(AHR). Methods : To examine the effects of KSE on asthma, mice were sensitized with $100{mu}g$ of OVA and 1 mg of aluminum potassium sulfate(Alum; Sigma)intraperitoneally on day 0 and 7. On day 14, mice were challenged on 3 consecutive days with 5% OVA and AHR was assessed 24 hrs after the last challenge. To examine severity of AHR, I examined eosinophil population and cytokine production in bronchoaveloar lavage fluid(BALF) and stained with hematoxylin and eosin in lung and also measured enhanced pause(Penh) in AHR from mice. Results and Conclusion : KSE potently inhibited the development of Penh and also reduced the number of eosinophil during OVA-induced AHR. KSE also inhibited cytokines production such as IL-4, IL-5 in BALF. Furthermore, KSE inhibited percentage of eosinophil in BALF. These results suggest that KSE may be beneficial oriental medicine for AHR.