The purpose of this study was to determine effective cut-off values of waist circumference (WC) to detect the clustering of cardiovascular risk factors (CCRF) in a Japanese population. The subjects were 2,476 men and women who participated in a health examination in Tokyo. The CCRF was defined according to the International Diabetes Federation (IDF) and the Japanese Committee of the Criteria for Metabolic Syndrome (JCCMS). The effective (accurate and sensitive) values were tested using the receiver operating characteristics analysis. The accurate (maximised sensitivity plus specificity) values were 81 cm and 80 cm using the IDF and JCCMS criteria for men, and 82 cm for both criteria for women. From the ROC curve, 85 cm was identified as an effective value for men. Thus, the effective cut-off value of WC for the Japanese should be approximately 85 cm for men and approximately 82 cm for women.