Clinical hyperglycaemia affects vascular endothelial function, but the effect on shear stress-induced arterial dilatation has not yet been established. We hypothesised that hyperglycaemia inhibited this response via impaired glycocalyx mechano-transduction. Experiments were carried out in the anesthetised pig in which pressure, blood flow and diameter of the left iliac artery were measured at two sites proximal (d1) and distal (d2). Infusion of glucose, sufficient to raise blood glucose to 16 - 30mM along the whole length of the artery, attenuated the shear stress-dependent dilatation in both sections of the artery with preservation of the responses to acetylcholine. D2 was then isolated using snares and the lumen exposed to blood containing 25 - 35mM glucose for 20min. In the control situation, after exposure of the distal section (d2) to normoglycaemia (5.7mM glucose), both sections of artery showed increases in diameter in response to shear stress and acetylcholine. Hyperglycaemia attenuated the shear stress dependent dilatation in the distal section only (p<0.25), but not the response to acetylcholine. It is concluded from these results that the hyperglycaemia impaired dilation is consistent with loss of mechanotransducing properties of the endothelial glycocalyx by hyperglycaemia. These findings offer a possible explanation for the increased incidence of vascular disease in diabetic patients.