Hydrogen sulphide (H2S) is endogenously produced in vascular tissue and has anti-oxidant and vasoprotective properties. This study investigates whether chronic treatment using the fast H2S donor NaHS could elicit a vasoprotective effect in diabetes. Diabetes was induced in male C57BL6/J mice with streptozotocin (60mg/kg daily, ip for 2weeks) and confirmed by elevated blood glucose and glycated haemoglobin levels. Diabetic mice were then treated with NaHS (100 mu mol/kg/day) for 4weeks, and aortae collected for functional and biochemical analyses. In the diabetic group, both endothelium-dependent vasorelaxation and basal nitric oxide (NO center dot) bioactivity were significantly reduced (p<0.05), and maximal vasorelaxation to the NO center dot donor sodium nitroprusside was impaired (p<0.05) in aorta compared to control mice. Vascular superoxide generation via nicotine adenine dinucleotide phosphate (NADPH) oxidase (p<0.05) was elevated in aorta from diabetic mice which was associated with increased expression of NOX2 (p<0.05). NaHS treatment of diabetic mice restored endothelial function and exogenous NO center dot efficacy back to control levels. NaHS treatment also reduced the diabetes-induced increase in NADPH oxidase activity, but did not affect NOX2 protein expression. These data show that chronic NaHS treatment reverses diabetes-induced vascular dysfunction by restoring NO center dot efficacy and reducing superoxide production in the mouse aorta.