Sulodexide, a glycosaminoglycan-containing compound, is known to have an antiproliferative effect on vascular smooth-muscle cells, in vitro, as well as antithrombotic and fibrinolytic effects. But there are few reports about the effect of neointimal proliferation in vivo. In this study, we examined whether Sulodexide was effective in the inhibition of neointimal proliferation after vascular injury. Ten-week-old Sprague-Dawley rats were subjected to vascular injury by endothelial denudation of the common carotid artery by using a balloon catheter. They were then allocated randomly into a control group (saline 2 ml for 3 days, and then 1 ml for 18 days, IM) and a treated group (Sulodexide 10 mg/kg/day for 3 days, and then 4 mg/kg/day for 18 days, IM). Three weeks after vascular injury, we analyzed the neointimal proliferation using morphometry. The neointimal proliferation was significantly reduced in the treated group compared to the control group (Ratio of neointimal area to medial area; 118.39 ± 6.80% in the treated group, 177.25 ± 17.25% in the control group). This result showed that Sulodexide might be effective in reducing the rate of restenosis after balloon angioplasty.