Although high on-treatment platelet reactivity (HTPR) is an important predictor of clinical outcomes in patients undergoing coronary stenting, it is unknown whether endothelial dysfunction and HTPR are associated. We examined the platelet function, peripheral vascular function, endothelial progenitor cell (EPC) number, platelet activation markers, high-sensitivity C-reactive protein (hs-CRP) level, and clinical outcomes in patients receiving chronic clopidogrel therapy. We consecutively enrolled 91 patients who underwent follow-up angiography because of chest discomfort. All patients took aspirin and clopidogrel for an average of 498 ± 138 days. Platelet reactivity was assessed by light transmittance aggregometry (maximal platelet aggregation by 5 μmol/L of adenosine diphosphate ≤50% in group 1 [optimal response] and >50% as group 2 [HTPR]). Flow-mediated dilation of the brachial artery and brachial-ankle pulse wave velocity (PWV), numbers of EPCs isolated from peripheral blood, platelet activation markers (soluble CD40 ligand and soluble P-selectin), and hs-CRP levels were assessed before follow-up angiography. There were no significant differences in baseline characteristics and previous percutaneous coronary intervention (PCI) data between groups 1 (n = 59) and 2 (n = 32). Group 2 showed poorer flow-mediated dilation (6.1 ± 4.1% vs 12.9 ± 6.2%, p <0.001), pulse wave velocity (1925.4 ± 362.2 vs 1571.0 ± 306.5 ms, p <0.001), and lower circulating EPCs by flow cytometry (21.9 ± 14.7 vs 65.2 ± 30.1 per 10 fields, p <0.001) compared with group 1. Significantly higher levels of soluble CD40 ligand, soluble P-selectin, and hs-CRP were observed in group 2. In multivariate analysis, elevated hs-CRP level, but not HTPR, was independently associated with repeated PCI. In patients with angina, HTPR was associated endothelial dysfunction and elevated hs-CRP, although elevated hs-CRP level was significantly associated with poorer outcomes.