Backgrounds Exercise improves endothelial function through increased numbers of circulating endothelial progenitor cells(EPC). We investigated even single bout hiking improves endothelial function, arterial stiffness and EPC. We measured the number of circulating EPC, and tested vascular health by flow-mediated dilation (FMD), brachial-ankle pulse wave velocity (baPWV), Augmentation Index (AIx) before and after hiking. Methods 24 young healthy volunteers were enrolled. They hiked the Seorak mountain (1708m height, 16km long, 11 hours 20 minutes distance by walk) together once this summer. We tested FMD, baPWV, AIx and measured EPCs (CD34/KDR, CD34/CD117, CD34/CD133) at baselines and immediate after hiking. Results 16 volunteers were male (67%) and mean age was 27.3(짹5.7). mean BMI(body mass index) was 21.4(짹3.4) and they did not have medical history including hypertension and diabetes mellitus. After moderate degree hiking, FMD and AIx improved significantly compared with baseline. (P=0.001, 0.003, respectively) (figure 1). Absolute numbers of all EPCs improved significantly after hiking. (all EPCs, P<0.001) (figure 2). There is no significant difference of blood pressure and baPWV (table). Conclusions Even single bout hiking improved vascular endothelial function and arterial stiffness and augmented the number of circulating EPCs in young healthy volunteers.