The pathogenic mechanism of diabetic peripheral neuropathy is multifactorial. This study investigated microangiopathic changes of endoneurial vessels of sural nerve in Vacor-induced diabetic rats. Experimental rats were divided into 3 groups: acute (80 mg/kg, once), chronic diabetic (8 mg/kg, 14 times), and control. Ultrastructural morphometric parameters of endoneurial microvessels, blood glucose, and body weight changes were statistically analyzed, and correlations among the variables were evaluated. The body weight and blood glucose levels were significantly different between the control and diabetic rats. The blood glucose was more significantly elevated in the acute diabetic rats than the chronic diabetic rats. Inner and outer vascular circumference, vascular area, luminal area, basement membrane area, and basement membrane thickness were significantly increased in the acute diabetic rats compared to the control group, but not between the chronic diabetic rats and the control group. The thickness of basement membrane was positively correlated with hyperglycemia and body weight loss ( P <. 01). These results suggest that the microangiopathy of the peripheral nerve could be developed in acute Vacor-induced diabetes. The decreased perfusion through microangiopathic endoneurial vessels appears to have a pathogenic role causing diabetic peripheral neuropathy.