Background and Aim: Previously, we have demonstrated that HMC05, a water extract from 8 medicinal herbs, has anti-inflammatory and anti-atherosclerotic effects. One notable finding was the preservation of the smooth muscle cell layer by HMC05 in high-fat high-cholesterol fed apoE-/- mice. Hsp27 expression was shown to be decreased in the advanced atherosclerotic plaque of human caroitid arteries. In this study, we have investigated whether HMC05 and Hesperidine, a single compound derived from HMC05, can affect restenosis using balloon injury model in rats, and smooth muscle cell migration in scratch model in vitro. Also we tried to investigate the role of Hsp27 in the inhibition of neointima formation. Methods and Results: To induce neointima formation, the right carotid artery of Male Sprague-Dawley rats (400~450g) was exposed, inserted with a 2F Fogarty catheter in an defined arterial segment, and then the endothelium was denuded by moving the catheter back and forth 3-4 times. HMC05 (160mg/kg/day) was administered by tube feeding starting from 4days before surgery and continued for 2 weeks after carotid injury. Injured carotid arteries isolated from rats were embedded in paraffin block and tissue sections were stained with H&E to assess neointima formation. Although there was no significant difference in medial area between control and HMC05 treated group (Control: 0.93mm2, HMC05: 0.92mm2), intima to media ratios was 37.25-fold lower in rats treated HMC05 than in control rats. Immunohistochemistry and confocal analysis confirmed that medial smooth muscle cells of arterial wall from rats treated with HMC05 showed significant overexpression of HSP27 compared with that of control rats. In addition, cell migration was dramatically inhibited when rat vascular smooth muscle cells (RVSMC) were treated with HMC05 or Hesperidine in the scratch model in culture dish. Conclusions: HMC05 and Hesperidine, a medicine from oriental herbs, showed significant inhibition of neointima formation in rat carotid artery balloon injury model. Hsp27 overexpression in the medial smooth muscle cells in HMCO5 or Hesperidine treated rats may play important roles in inhibiting smooth muscle cell migration and proliferation.