Excess waist circumference (WC) is a frequently used indicator of abdominal obesity and/or cardiovascular disease (CVD) risk. Nonetheless, search of the literature revealed no prospective studies on the association between WC and CVD events in diabetic patients. In this study, the clinical significance and implications of WC as a cardiovascular and metabolic risk indicator was prospectively investigated in Japanese patients with type 2 diabetes. For this purpose, baseline data on WC, hypertension, and dyslipidemia were collected and subsequent CVD (coronary heart disease and stroke) events during the following 8 years were studied in 1,424 Japanese type 2 diabetic patients, and the cross-sectional/longitudinal associations between WC and CVD risk factors/events were analyzed. Mean WC levels were significantly increased according to the number of coexisting risk factors. However, no significant difference in mean WC between subgroups with and without CVD events was noted, and excess WC alone was not predictive of subsequent CVD events either in male or female subjects even after adjustment for age, smoking, hypertension, and dyslipidemia. In female patients, excess WC (> or =80 cm) was predictive of CVD events only with the coexistence of hypertension. In Japanese diabetic patients, excess WC alone, although a good marker for clustering of CVD risk factors, did not raise the risk of CVD events unless accompanied by hypertension in female patients. Further investigations are necessary before WC as a risk factor can be utilized in clinical settings for the management of diabetes in this population.