Abstract: Objective: To determine if Endovascular radiation will be effective in inhibiting vascular remodeling after coronary intervention. Methods: Twelve swine underwent coronary balloon overstretch. The radiation delivery system was used to deliver 20 Gy to dilated segment in the seven swine. All animals were given aspirin （325 mg） daily and were killed at 30 days. Cross sections were used to perform computer-based morphometric analysis and immunohistochemistry（α-actin） stain. Results: Vessel perimeter, lumen perimeter, and lumen area were increased significantly in the irradiated segments. There were fewer α-actin positive cells in the adventitia of the irradiated vessels than in nonirradiated controls. Conclusion: Endovascular radiation demonstrated a favorable effect on late remodeling by reducing α-actin positive cells and preventing the fibrosis in the adventitia.