BACKGROUND AND OBJECTIVES: Vascular brachytherpy known to be an effective method in the prevention of restenosis following percutaneous coronary intervention (PCI). In this study we observed the effects of a radioisotope-loaded stent in a porcine model. MATERIALS AND METHODS: Holmium-166 ((166)Ho) was loaded onto the stent surface using impregnated polyurethane, and placed the stents into 7 porcine coronary arteries. Four weeks after stent overdilation injury, histopathological examination was performed. RESULTS: The absorbed dose of (166)Ho to the coronary artery, from the 158.5+/-140.9 microCi (166)Ho stent, was about 141 Gy at a depth of 0.5 mm, which was calculated by Monte Carlo EGS 4 Code. The mean external, and internal elastic lamina areas, the luminal and neointimal areas and the histopathological area stenosis in the 7 porcine coronary arteries were 7.6+/-2.8 mm2, 4.7+/-1.6 mm2, 2.4+/-1.4 mm2, 2.3+/-1.6 mm2 and 49.4+/-24.9%, respectively. The histopathological findings revealed remarkable inflammatory reactions and thrombosis in two of the porcine coronary arteries. CONCLUSION: (166)Ho radioactive loaded stents, using impregnated polyurethane, may inhibit neointimal hyperplasia, but the problems of stent thrombosis and inflammation should be solved.