The aim of the study was to evaluate the effect of metformin on markers of endothelial function, vascular inflammation and factors of thrombosis in obese type 2 diabetic patients. Twenty-four type 2 diabetic patients (15 female, 9 male) previously under medical nutrition treatment (MNT) + regular exercise programme (REP) without chronic micro or macrovascular complications with the mean age of 50.5 +/- 1.5 years, diabetes duration of 17.9 +/- 6.3 months and body mass index (BMI) of 31.7 +/- 0.8 kg/m(2) were enrolled in the study. In the first 4 weeks, all the patients continued MNT + REP. In the following 12 weeks, metformin (mean daily dosage of 1381 +/- 85 mg) was added. After the first period with MNT + REP, BMI, waist circumference, fat percentage, blood pressure and HDL cholesterol decreased significantly. After metformin addition, there was a significant decrement in BMI, waist circumference, fat percentage, fasting and postprandial. plasma glucose, hemoglobin A1C, plasminogen activator inhibitor-1 (PAI-1), vascular endothelial growth factor (VEGF) and increment in P cell reserve values of the patients. Our results indicated that, metformin addition had beneficial effect on VEGF and PAI-1 levels in obese type 2 diabetic patients under MNT + REP, independent from its' favourable effects on BMI and glycemic control. (C) 2008 Elsevier Ireland Ltd. All rights reserved.