PURPOSE OF REVIEW: Intradialytic nutritional support has been used for more than 30 years both in critically ill patients with acute renal failure and during maintenance hemodialysis. Present knowledge allows better estimation of its metabolic and nutritional efficacy, as well its effect on patient outcome. RECENT FINDINGS: Recent data showed that intradialytic nutritional support is able to counteract these effects of dialysis on protein metabolism and to improve both nitrogen and energy balance. In maintenance hemodialysis patients, the improvement of nutritional status during nutritional support was shown to improve long-term survival. In critically ill patients with acute renal failure, protein sparing is one of the main therapeutic goals. The effect of nutritional support on patient outcome is not demonstrated. Recent data, however, showed that the improvement of nitrogen balance may be associated with a better outcome. SUMMARY: Current information helps to better assess the effects of intradialytic nutritional support, to clarify the nutritional management of renal failure patients and to provide recommendations. Future research should focus on the possible means to improve the efficacy of nutritional support, either by modifying its components of by associating anabolic or anticatabolic agents.