The incidence of diabetes is increasing, and the disease has become an important predictor of prognosis in patients with coronary artery disease (CAD), although adverse events often occur without warning. Thus, risk stratification of diabetic CAD patients is important for secondary prevention. This study tests the hypothesis that brachial-ankle pulse wave velocity (baPWV), a marker for arterial stiffness obtained by simple and noninvasive automated devices, can be a risk stratification index to predict prognosis in diabetic patients with CAD. The prognosis of CAD patients with diabetes in the Shinken Database cohort study was investigated by dividing patients into two groups based on baPWV measurements. The composite endpoint was death, nonfatal myocardial infarction, repeat revascularization or readmission for heart failure. Data were available on 564 CAD patients, with a median follow-up of 25.4 months. Of these patients, 191 had type 2 diabetes. The higher baPWV among diabetic patients was defined as a median baPWV of 1730 cm s(-1) or more. The 3-year Kaplan-Meier estimates of event-free survival were 72.8% in diabetic patients with lower baPWV and 51.3% in those with higher baPWV, respectively (P=0.031). Multivariate analysis revealed that a higher baPWV was independently associated with poorer short-term prognosis (hazard ratio, 1.97; 95% confidence interval, 1.01-3.84) in diabetic CAD patients. In conclusion, baPWV, a marker for arterial stiffness, can be a risk stratification index for short-term prognosis in clinical practice, suggesting the need for further aggressive treatment and strict follow-up in CAD patients with diabetes and higher baPWV.