Oxidative stress is linked to the pathogenesis of the major complications of diabetes in the kidney, the heart, the eye or the vasculature. Members of the Nox family of NADPH oxidases are a major source of reactive oxygen species and are critical mediators of redox signalling in cells from different organs afflicted by the diabetic milieu. In this Review, the authors provide a comprehensive overview of the current knowledge related to the understanding of the role of Nox in the processes that control cell injury induced by hyperglycaemia and other predominant factors enhanced in diabetes.