Over the last 10 years there have been substantial changes in the issues confronting intensivists and surgeons caring for critically ill patients. A substantial increase in the number of elderly patients with surgical illness and complex co-morbidity has accompanied the increase in the proportion of elderly in populations in the developed world. This phenomenon has been seen particularly with sepsis. Incidence rates for blunt trauma have declined overall, but the problems of the elderly trauma patient have become more evident. Major elective surgery remains a common indication for short-term intensive care in many countries, but the need for cost-containment has led to increased use of high-dependency care for many such patients. Expectations of both society and clinicians have increased, and this has been reflected in the increased demand for complex procedures (e.g., liver transplantation, cerebral artery aneurysm clipping, aortic aneurysm repair) in patients previously considered at too high risk. Along with these expectations have come pressures on clinicians to reduce costs at the same time as improving clinical outcomes. Despite many advances in the care of critically ill patients with injury or sepsis, mortality, morbidity, and cost remain high; and nutritional support is frequently required. The duration and extent of the metabolic changes seen in response to critical surgical illness and intensive care treatments have become better characterized. Although some of the changes in body water and fat are modifiable, loss of large amounts of (functional) protein has been resistant to various strategies so far studied.