Stress-induced hyperglycaemia is a significant problem in critically ill patients, including those with surgical or traumatic injury in the intensive care unit (ICU). The severity of hyperglycemia and insulin resistance reflect the risk of death. A recent, large, prospective, randomized, controlled study showed that maintaining normoglycemia with intensive insulin therapy improves survival and reduces morbidity in a surgical ICU population. Recent data from observational studies has confirmed the clinical benefits of glycaemic control in both surgical and mixed surgical/medical ICU conditions. Titrating insulin to normoglycaemia appears to be crucial in order to achieve most clinical benefits. Prevention of glucose toxicity protects the endothelium as well as ultrastructure and function of hepatocyte mitochondria. Other metabolic and non-metabolic effects of the insulin administered contribute to the clinical benefits, including a partial correction of the deranged serum lipid profile, prevention of excessive inflammation and immune dysfunction and a counter-action to the catabolic state.