Purpose of reviewThis review intends to summarize the recent findings regarding the presence of increased oxidative stress in critically ill patients and its potential pathophysiologic role, as well as the results of recent clinical trials of antioxidant therapies.Recent findingsSeveral lines of evidence confirm the increase in oxidative stress during critical illness. The oxidative damage to cells and tissues eventually contributes to organ failure. Prophylactic administration of antioxidant vitamins or glutamine, incorporated in the nutritional support or given as separate medications, efficiently attenuates the oxidative stress and in some studies improves the outcome of critically ill patients. Few data on the effects ofN-acetylcysteine or trace elements have been published during the last two years.SummaryPatients at risk of organ failure could benefit from the early adjunction of antioxidant treatment, including vitamins and glutamine.