INTRODUCTION: Endothelium-dependent dilation is improved in insulin-treated diabetic patients, but this effect is probably due to improved glycemic control. The objective of the present study was to compare endotheliumdependent dilation in patients with well-controlled type 2 diabetes who are or are not using insulin as part of their therapy. METHODS: We studied 27 patients with type 2 diabetes (11 women, 60.3 years ¡ 6 years, with HbA1c , 7% and no nephropathy), including 16 patients treated with anti-diabetic agents (No-Ins, 8 women) and 11 patients treated with insulin alone or in combination with anti-diabetic agents (Ins, 3 women). Endothelial function was evaluated by the dorsal hand vein technique, which measures changes in vein diameter in response to phenylephrine, acetylcholine (endothelium-dependent vasodilation) and sodium nitroprusside (endothelium-independent vasodilation). RESULTS: Age, systolic blood pressure (No-Ins: 129.4 mmHg ¡ 11.8 mmHg, Ins: 134.8 mmHg ¡ 12.0 mmHg; P = 0.257), HbA1c, lipids and urinary albumin excretion rate [No-Ins: 9 mg/24 h (0-14.1 mg/24 h) vs. Ins: 10.6 mg/24 h (7.5- 14.4 mg/24 h), P = 0.398] were similar between groups. There was no difference between endothelium-dependent vasodilation of the No-Ins group (59.3% ¡ 26.5%) vs. the Ins group (54.0% ¡ 16.3%; P = 0.526). Endotheliumindependent vasodilation was also similar between the No-Ins (113.7% ¡ 35.3%) and Ins groups (111.9% ¡ 28.5%; P = 0.888). CONCLUSIONS: Subcutaneous insulin therapy does not interfere with venous endothelial function in type 2 diabetes when glycemic and blood pressure control are stable.