Patients admitted to the ICU may be malnourished at the time of admission, and certainly become so under the catabolic stress of major illness. The malnourished patient suffers from a reduction in immunity and is predisposed to infections. The importance of providing nutrition to critically ill patients is now widely accepted. Recently there has been a move to introduce certain dietary compounds with immune-enhancing actions to the feed. Compounds that have been found to have such properties include glutamine, arginine, nucleotides and omega-3 polyunsaturated fatty acids. None of these compounds when added into immune-enhancing enteral feeds have been shown to improve survival when compared with standard enteral feeds. However, most studies have shown reduction in infection rate, number of days ventilated and length of hospital stay. All these immune-enhancing formulas are significantly more expensive than standard formulas. In York, we supplement standard enteral feeds with glutamine (p. 110).