Background and Objectives: We hypothesized that patients with nitroglycerin-induced headache had preserved systemic vasomotion and there might be an increased nitroglycerin-mediated dilation (NMD) response in the brachial artery. The aim of this study is to evaluate whether nitroglycerin (NTG)-induced headache is associated with the level of the NMD and flow-mediated dilation (FMD) or the severity of coronary artery disease (CAD). Subjects and Methods: The study included 87 patients (Group I: mean age: 54.8±9.5 years, 46 males) with headache and new onset chest pain, and 109 patients (Group II: mean age: 57.4±8.9 years, 67 males) without headache and with new onset of chest pain. Patients were excluded from this study if they had a history of chronic headache, long term nitrates use and coronary artery procedures. Coronary angiography was performed within one month after administering nitroglycerin for the usual clinical indications. Results: The clinical characteristics did no