Cell-derived microparticles are supposed to be involved in endothelial dysfunction and atherogenesis. This study aimed to evaluate circulating microparticles in diabetic subjects with erectile dysfunction (ED) and their relation with endothelial dysfunction. Thirty diabetic men with ED and 20 age-matched control subjects without ED were assessed for circulating microparticles and endothelial dysfunction. Flow cytometry was used to assess microparticles by quantification of circulating endothelial (EMP, CD31(+)/CD42b(-)) and platelet (PMP, CD31(+)/CD42b(+)) microparticles in peripheral blood. Endothelium-dependent flow-mediated dilation (FMD) was evaluated in the right brachial artery after reactive hyperemia. Compared with non-diabetic subjects, diabetic men presented significantly higher numbers of EMP (P=0.001), and reduced FMD (P=0.01), with a significant inverse correlation between the number of circulating EMP and the International Index of Erectile Function (IIEF) score (r=-0.457, P=0.01). Multivariate analysis correcting for age, anthropometric indices, glucose and lipid parameters, FMD and PMP identified EMP as the only independent predictor for IIEF score (P=0.03). EMP are elevated in impotent diabetic subjects and independently involved in the pathogenesis of ED.