Background: Initial enthusiasm for DES has been tempered by a possible increased risk of stent thrombosis. One of the suggested mechanisms for this stent thrombosis is delayed re-endothelialization. Aptamers, capture molecules (oligonucleotides) for endothelial progenitor cells (EPCs), are able to recognize circulating EPCs and to bind them. Coating of bare-metal cobalt chromium stents with aminoparylene as a carrier substance and aptamer as an EPC-capturing oligonucleotide would be effective in the prevention of in-stent restenosis without increasing thrombus. Methods: To evaluate effects of aptamer-coated stents, six 20 kg-Yorkshire pigs were utilized. Three different intracoronary stents were implanted in the three epicardial coronary arteries [(1: cobalt-chromium (CC), 2: TAXUS (TA), 3: aminoparylene and aptamer-coated stent (AA)] in a random fashion at 8 to 10 atm. Stent length was 18 mm and stent diameter 3 mm. Four weeks after stenting, the animals were studied with follow-up coronary angiography and acetylcholine (10 ml, 3 關g/ml) stimulation tests for coronary spasm. After euthanization, the coronary arteries were harvested for histologic analysis and scanning electron microscopy. Results: All three stents showed similar minimal luminal diameters (MLD) at baseline. There was a decrease in MLD in all the three stents: CC (12.3짹5.5 %), TA (10.4짹3.7 %), and AA (11.2짹6.3 %) (p=NS). Neointimal hyperplasia (NIH) was similar in all three stents ranging between 1.77 짹0.57 mm² for CC, 1.83짹0.93 mm² for TA, and 1.78짹 1.69 mm² for AA (p=NS). Histologic restenosis was 32.07짹6.26 % for CC, 14.48짹9.03 % for TA, and 28.15짹15.35 % for AA (p=NS). During the Ach stimulation test, 1 severe spasm (total occlusion) in TA was detected at the proximal and distal stent edge. Re-endothelialization score was CC: 3.4, TA: 1.3, and AA: 3.6. Thrombus appearance rate was CC: 0 % TA: 66.7 %, and AA: 16.7 %. Conclusion: AA stents showed a tendency toward a lower incidence of stent thrombus without coronary spasm compared with TA. However, the inhibition of NIH was similiar between the 3 groups. Further histologic results will soon be presented.