Metabolic syndrome (MS) has been currently increasingly identified, and found to be associated with increased risk for cardiovascular events. Acute coronary syndromes (ACS) have considerable frequency along with increased morbidity and mortality among population. We searched the association of MS with extension of coronary artery disease (CAD) in patients presenting with non ST segment elevation (NSTE) ACS. We evaluated 306 consecutive patients with the diagnosis of NSTE ACS, hospitalised within the first 24 hours of their chest pain into coronary care unit, and noted components of MS. Coronary angiograms were evaluated according to Sullivan's method. MS was noted in half of all patients, and was more frequent in female patients than in male patients (62.8% v.s. 43.6%, P=0.003). Mean total stenosis and extension scores of patients with MS was significantly higher than those without MS. Presence of MS, poor total cholesterol/HDL cholesterol ratio, hypertension, diabetes mellitus, were found to be independently predictive of extension of CAD in a group of patients presenting with NSTE ACS. MS might account for CAD extension in patients with NSTE ACS.