BACKGROUND & AIMS: Malnutrition is a recognized risk factor for perioperative morbidity, but there is currently no standardized definition of malnutrition. The Nutrition Risk Screening 2002 score was recently proposed to identify patients at nutritional risk who may benefit from nutritional support therapy, and has been officially adopted by the European Society of Parenteral and Enteral Nutrition. The aim of this study was to assess the value of the Nutrition Risk Screening 2002 score in predicting the incidence and severity of postoperative complications in gastrointestinal surgery. METHODS: We prospectively evaluated 608 patients admitted for elective gastrointestinal surgery. Nutritional risk was defined by the Nutrition Risk Screening 2002 score and correlated to the incidence and severity of postoperative complications. Complications were classified using an established surgical complication classification. RESULTS: The overall incidence of nutritional risk was 14%. We observed a significantly higher complication rate of 40% (35 out of 87) in patients at nutritional risk, compared to 15% (81 out of 521) in patients with a normal score (p<0.001). The incidence of severe complications was significantly higher in patients at nutritional risk (54% versus 15%; p<0.001). The odds ratio to develop a complication was 2.8 in patients at risk (p=0.001), and 3.0 in patients with malignant disease (p<0.001). The median length of stay in nutritional risk patients was significantly longer (10 versus 4 days, p<0.001). CONCLUSION: The prevalence of nutritional risk patients in gastrointestinal surgery is high. We showed that nutritional risk screening using the NRS 2002 strongly predicts the incidence and severity of complications.