Background: The formation of advanced glycation end products (AGEs), in various tissues has been known to enhance the immunoinflammatory reaction and local oxidant stress in long standing diabetes. Recently, AGEs have been reported to play a role in neointimal formation in the animal model of arterial injury. We have investigated whether the serum levels of AGEs are associated with the coronary restenosis in diabetic patients. Methods: Blood samples were collected from the diabetic patients with coronary artery disease undergoing stent implantation and the serum levels of AGEs were analyzed by the fluorescent intensity method. The development of in-stent restenosis (ISR) was evaluated at 6 months follow-up coronary angiography. Results: Total 263 target lesions were evaluated in 203 patients. The ISR rate in the high-AGE (>170 U/ml) group (40.1%) was significantly higher than that in the low-AGE group (���170 U/ml) (19.6%) (p<0.001). Furthermore, the multivariate analysis has demonstrated that a high level of serum AGEs is an independent risk factor for the development of ISR (odds ratio, 2.659; 95% CI, 1.431-4.940; p=0.002). Conclusions: The serum levels of AGEs can be a good predictor for ISR and one of the guidelines for medical therapy and interventional strategy to prevent ISR in diabetic patients.