Integrated backscatter (IBS) signal obtained by extracranial ultrasound examination of the carotid artery can be used to evaluate the tissue characteristics of arterial plaque. To examine whether clustering of several cardiovascular risk factors, metabolic syndrome (MetS), affects the tissue characteristics of the carotid artery, we measured Calibrated-IBS values of the intima-media complex in the carotid artery for 142 patients (61.6+/-9.5 years old) with at least one component of MetS. Calibrated-IBS values were inversely correlated with the number of MetS components (r=-0.224, p=0.0073). Furthermore, the number of MetS components was an independent risk factor for a low Calibrated-IBS. The subjects with coronary heart disease (CHD) (n=20) showed significantly lower Calibrated-IBS than those without it (n=122) (-17.8+/-5.1 vs. -21.7+/-5.5 dB, p=0.0020), and the logistic regression analysis showed that the presence of CHD was associated with Calibrated-IBS (RR=0.898, 95%CI: 0.811-0.994, p=0.0374). These results suggest that clustering of the cardiovascular risk factors affects the Calibrated-IBS, an acoustic parameter of tissue characteristics of the intima-media complex in the carotid artery.