It has long been known that injury, infections and other critical illnesses are often associated with hyperglycemia and hyperinsulinemia. Mortality of critically ill patients is greatly reduced by intensive insulin therapy, suggesting the significance of reversing or compensating for the development of acute insulin resistance. However, the development of acute injury/infection-induced insulin resistance is poorly studied, much less than the chronic diseases associated with insulin resistance, such as type 2 diabetes and obesity. We previously found that insulin resistance develops acutely in the liver after trauma and hemorrhage. The present study was designed to begin to understand the first steps in the development of trauma and hemorrhage-induced acute hepatic insulin resistance in an animal model of injury and blood loss similar to traumatic or surgical injury and hemorrhage. We present novel data that indicates that hepatic insulin resistance increased dramatically with an increasing extent of hemorrhage. With increasing extent of blood loss, there were increases in serum TNF- levels, phosphorylation of liver IRS-1 on serine 307, and liver c-Jun N-terminal Kinase (JNK) activation/phosphorylation. Exogenous TNF- infusion increased JNK phosphorylation and IRS-1 serine 307 phosphorylation, and inhibited insulin-induced signaling in liver. Conversely, a neutralizing TNF- antibody treatment reversed many of the hemorrhage-induced changes in hepatic insulin signaling. Our data indicate that the acute development of insulin resistance following trauma and hemorrhage may have some similarities to the insulin resistance that occurs in chronic diseases. However, since so little is known about this acute insulin resistant state, much more needs to be done before we can attain a level of understanding similar to that of chronic states of insulin resistance.