Protein-energy undernutrition, or the possibility of its development, has been documented to occur frequently in surgical patients admitted to hospital. Nutritional status is known to deteriorate over the course of the hospital stay, with poor awareness by medical and nursing staff as to the deleterious effects of impaired nutritional status on clinical outcome and hospital costs. While there is no consensus on the best method for assessment of the nutritional status of surgical patients pre-operatively, there are a number of techniques available. These techniques can be divided into two types, those suitable for screening for nutrition risk on admission to hospital and those used to fully assess nutritional status. Both techniques have their limitations, but if used correctly, and their limitations recognized, should identify the appropriate degree of nutritional intervention for an individual patient in a timely and cost-effective manner. The techniques currently available for nutritional screening and nutritional assessment are reviewed, and their applicability to the Irish setting are discussed in the present paper.