Denutrition decreases immunological responses of non-cancer patients, the healing is altered whereas infectious complications increase. Now during hospitalization, malnutrition prevails in cancer patients. The suppression of the adaptability to fasting which reduces the expenditure of energy at rest, an a normal metabolic response to nutrients' supply with the impossibility to compensate totally the metabolic deficits with the artificial nutrition alone, raise the fear of postoperative disorders, particularly an increase of the infectious risk. The key point is therefore to identify the cachexia's degree owing to a simple, predictive and consensual index. This check-up allows a postoperative complications' prevention by starting up a perioperative refeeding in high-risk subjects: that is to say all severe wasting patients, the people booked for a severe surgical procedure, especially for oesophageal and gastric neoplasms. Actually, we consider that the quality of the results depend more on the making up of the different nutritional solutions dispensed than to strictly providing for cancer patients' wants, which could be harmful in the postoperative period. Supplementation with antioxidant micronutrients or arginine, glutamine, ribonucleic acids and omega-3 fatty acids would allow an immuno- modulation of the renutrition. But complications strictly due to preoperative denutrition are still to be established.