Coronary endothelial vasodilator dysfunction is associated with increased cardiac events; the close relation between coronary vasomotor dysfunction and brachial artery vasoreactivity has been previously described. This study assessed the prognostic value of noninvasively assessed brachial artery vasoreactivity in survivors of acute coronary syndromes without ST-segment elevation. We examined 98 men (63.1 +/- 10.8 years) who were referred to our hospital for acute coronary syndromes without ST-segment elevation. Brachial artery endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent nitrate-mediated dilation were examined in all patients using high-resolution echocardiographic Doppler ultrasound within 24 hours of admission. Plasma malondialdehyde, a marker of oxidative stress, and left ventricular ejection fraction were also assessed. Twenty-seven patients underwent coronary revascularization. Patients were followed for 24.8 +/- 5.9 months. Cardiovascular death, myocardial infarction, stroke, and unstable angina were designated as cardiovascular events (CEs). Twenty CEs were recorded. Kaplan-Meyer analysis showed that patients with FMD <1.9% (tertile 1 of FMD values) were more likely to have CEs than those with FMD >1.9% (log rank 5.29, p = 0.021). Multivariate Cox regression analysis showed that FMD <1.9% predicted CEs with an adjusted hazard ratio of 3.035 (95% confidence interval 1.148 to 8.023, p = 0.025) after adjustment for age, risk factors, troponin T, ejection fraction, revascularization procedures, number of diseased vessels, and medication. In conclusion, endothelium-dependent dilation of the brachial artery is a strong independent predictor of adverse outcome in survivors of acute coronary syndromes without ST-segment elevation.