Objective: To evaluate the relationship between insulin resistance and endothelial function in type 2 diabetes patients withor without microalbuminuria and to explore the pathophysiological mechanisms of the increased macrovascular risk in type 2diabetes mellitus. Methods: Twelve type 2 diabetes patients with microalbuminuria (urinary albumin 30-300_g/mg creatinine,DM-MA) and 12 type 2 diabetes patients without microalbuminuria (urinary albumin <30_g/mg creatinine, DM-NA) wererecruited, matched for their sex, age, body mass index (BMI), diabetes duration, antidiabetic therapy. Their hemoglobin (HbA1C)was less than 7.5% and the blood pressure was lower than 140/90 mmHg. None had evidence of macrovascular disease and serumcholesterol levels were normal. Twelve healthy volunteers (C) were enrolled as controls. All subjects received a hyperinsulinemiceuglycemic clamp study (insulin infusion rate, 120 mU/m2/min) to assess the peripheral glucose disposal rate (GDR) in thesteady state and had a high-resolution ultrasonography to measure vasodilation in the brachial artery diameter in responseto reactive hyperemia (endothelium-dependent) and administration of glyceryl trinitrate (endothelium-independent). Plasmafree fatty acids (FFAs), plasminogen activator inhibitor type I (PAI-1), and von Willebrand factor (vWF) were also measured.Results: The GDR was lower in type 2 diabetes patients with microalbuminuria (7.90