Hyperglycemia is common in critically ill humans. Recent clinical trials have shown a significant reduction in morbidity and mortality rates with the use of intensive insulin therapy to maintain strict normoglycemia in critically ill patients. Hyperglycemia is associated with many detrimental effects, including reduced immune function, increased inflammation and coagulation, and modulation of the endothelium. Most of the evidence regarding the adverse effects of hyperglycemia is derived from humans with diabetes, cardiac failure, or traumatic brain injury. In addition to its anabolic effects on metabolism, insulin has antiinflammatory properties. To define the potential risks and benefits of intensive insulin therapy in critically ill animals, prospective, randomized clinical trials are necessary.