Background: Autonomic dysfunction is thought to be an important mechanism of metabolic syndrome (MetS), but there has not been a study on the direct association between MetS and heart rate (HR) in Japanese. Methods and Results: The association between MetS and HR was examined using medical check-up data from 1,880 men and 1,079 women. HR was significantly higher in MetS subjects than in non-MetS subjects in both men and women (P<0.0001 in men, P<0.001 in women). The prevalence of MetS increased linearly through the quartiles of HR in both men and women. HR was significantly correlated with MetS-related risk factors other than uric acid in men and other than uric acid, body mass index, waist circumference, and high-density lipoprotein cholesterol in women. Conclusions: The prevalence of MetS increased linearly with the increase in HR among Japanese men and women, and HR was significantly correlated with MetS-related risk factors. (Circ J 2009; 73: 1431 - 1436)