Objective To evaluate the efficacy of antiplatelet aggregation drugs (aspirin and clopridogrel) in in-stent restenosis (ISR) after percutaneous transluminal angioplasty and stenting (PTAS) by using thromboelastography (TEG) to assess the inhibitory rates of platelet aggregation. Methods Clinical data of 49 patients who were rehospitalizated in 6 to 12 months after PTAS for conventional re-evaluation by digital subtraction angiography (DSA) and TEG, and 6 patients with recurrent ischemic stroke (infarction or transient) after intra-or extra-cerebral stent placement in Jinling Hospital in November 2010 to May 2012 were collected. All patients were assessed the inhibitory rates of arachidonic acid (AA) pathway and adenosine diphosphate (ADP) receptor pathway in platelets by TEG. DSA confirmed 14 ISR among 64 lesion vessels treated with stents (ISR group). Potential variables for restenosis and the inhibitory rates of AA pathway and ADP receptor pathway in platelets were analyzed for any predictive power for the ISR with SPSS version 15.0. Results (1) There was significant difference in male-to-female ratio between recurrent stroke group (male/female∶1/5) and non-recurrence group (male/female: 39/4; P＜0.01). The serum concentrations of high-sensitivity C reactive protein (hs-CRP) in patients with recurrent stroke were higher than those without recurrence [(8.9±11.0) vs (2.9±4.1) mg/L, P＜0.05)]. The differences of other variables between recurrent and non-recurrent groups were not significant (P＞0.05). (2) Compared with non-ISR (control) group, variables in ISR group including age [(58.0±12.8) vs (64.6±9.8) years], the ratio of diabetes, and the ratio of lesion distributions in intra-and extra-cranial vessels (6/14 vs 7/14, 7/50 vs 43/50) were all significantly different (P＜0.05). Moreover, the serum concentration of hs-CRP was remarkably higher in ISR group than in non-ISR group [(6.1±7.6) vs (2.1±2.1) mg/L, P＝0.028]. Additionally, inhibitory rates of AA pathway and ADP receptor in patients with ISR were (58.0±43.8)% and (28.1±26.1)% whereas those in patients without ISR were (83.4±23.1)% and (52.8±29.5)% respectively, with significant difference (P＜0.01). (3) Logistic regression analysis showed that the inhibitory rate of ADP receptor or efficacy of clopidogrel (HR＝0.959; 95% CI 0.921～0.998; P＝0.039) was the only independent negative predictor for ISR after adjustment of the influence of other variables. Conclusion Despite the differences of several variables are significant including age, diabetes, distribution of lesion location, serum concentration of hs-CRP, and efficacy of aspirin and clopidogrel between ISR and non-ISR groups, only the inhibitory rate of ADP receptor in platelets or efficacy of clopidogrel is associated with decreased risk of ISR.