This chapter is complementary to the others in this volume focusing on preoperative fasting routines. In it we discuss some of the issues in need of more research to define best practice. One of these is the role of fasting in emergency patients. Modern preoperative fasting recommendations almost exclusively deal with elective patients. In emergency patients preoperative fasting cannot secure gastric emptying to reduce the risk of pulmonary aspiration. Hence, surgery should be timed according to the urgency of the situation, and the patient should always be treated as if the stomach was full. More data are needed to better define what is going on in the gastrointestinal tract during the perioperative period in these patients. In certain patient groups--such as patients with diabetes, gastro-oesophageal reflux disease and/or obesity--the data are insufficient to give complete guidance to best practice. Preoperative fasting guidelines also affect fluid balance and perioperative fluid management, a topic of debate in recent years. In addition, carbohydrate-enriched fluids for oral use in the preoperative phase have been shown to have a positive effect on postoperative metabolism. Recent studies also suggest that the immune system would be less affected by surgery with such preparations. Last but not least, new scientific evidence alone is not enough to change daily practice. Active implementation of new evidence is also needed. To improve perioperative care, anaesthesiologists, surgeons and the nursing staff must work together.