We strived to characterize the endothelial function status in type 2 diabetic patients with peripheral artery disease which was detected by ankle-brachial index by utilizing high frequency ultrasounds. Predictors of endothelial dysfunction were investigated. We chose 23 type 2 diabetic patients had ankle-brachial index <0.97 (0.15-0.95; mean=0.74+/-0.20), 31 diabetic patients had ankle-brachial index >/=1.0 and 28 non-diabetic subjects for study. Older age, a longer duration of diabetes, higher systolic blood pressure, higher prevalence of history of hypertension were observed in patients with peripheral vascular disease. Type 2 diabetic patients showed impaired flow-mediated dilatation than non-diabetic and it showed more impaired in patients with peripheral vascular disease. Nitroglyerin-induced dilatation showed a trend of impairment in patients with peripheral vascular disease but did not reach statistical significance. Age (r=-0.259, P=0.019), baseline brachial artery diameter (r=-0.321, P=0.003), ankle-brachial index (r=0.259, P=0.002) and hypertension history (P=0.01) were significantly associated with flow-mediated dilatation. However, after adjusting for age, only baseline diameter and ankle-brachial index were independent predictors of flow-mediated dilatation. In conclusion, we demonstrated flow-mediated dilatation was impaired in type 2 diabetic patients and it was further impaired in patients with peripheral vascular disease. Nitroglycerin-induced dilatation showed a trend of impairment but did not reach statistical significance.