Background: Although many clinical predictors of stent thrombosis (ST) have been reported, little is known about the role of genetic factors in the occurrence of DES thrombosis. To address these issues, we analyzed 3 candidate genetic variations related to vascular inflammation and platelet aggregation from patients enrolled in the multicenter Korean Stent Thrombosis (KoST) registry and matching controls. Method: The KoST registry was a multicenter study of 10 major medical centers in Korea, where we collected data of consecutive ST patients who underwent DES implantation from May, 2003 through Dec, 2006. All information were sent to a core center. The clinical, angiographic and procedural characteristics of 78 ST patients were compared with a control group of 3,599 patients who had at least 6 months of clinical follow-up. For genetic analysis in 71 ST patients with genomic DNA available and 244 matched control patients, two polymorphisms involved in platelet aggregation (P2Y12 -iT744C and P2Y1 A1622G) and one in inflammation (MCP-1 -A2578G) were analyzed. Results: ST patients were younger and were less likely to have hypertension and dyslipidemia than control patients. ST patients had more type 1 bifurcation lesions. The stent length, diameter and number were not different between the two groups. In the genetic analysis, the proinflammatory G/G genotype of MCP-1 gene was an independent predictor of DES thrombosis(OR 5.84; 95% CI 1.69-20.11; P=0.005) in a multivariate analysis, while two gain of function genotypes of platelet ADP receptor was not associated with ST, P2Y12 -i744C allele(OR 0.67; 95% CI 0.29-1.56; P=0.352) and P2Y1 1622G allele(OR 0.73; 95% CI 0.36-1.48; P=0.39). Conclusion: The vascular proinflammatory G/G genotype of MCP-1 gene rather than genotypes of platelet hyperfunction was an independent predictor of DES thrombosis in this cohort of Korean patients. Our findings suggest that genetic factors of inflammation may be involved in the risk of DES thrombosis.