The effects of endotoxemia on glutamine metabolism by the splanchnic bed was studied in vivo in adult rats 12 hours following administration of E. coli LPS. Glutamine uptake by the portal-drained viscera fell in the endotoxin-treated animals while glucose uptake doubled. Simultaneously, hepatic glutamine uptake increased ten-fold owing to both an increase in hepatic blood flow and glutamine extraction from the bloodstream. Hepatic alanine uptake, oxygen consumption, and glucose release were also accelerated in endotoxemic rats. The increase in liver glutamine utilization was associated with increases in parenchymal DNA and glutathione levels and an increase in glutathione and urea release into the systemic circulation. This marked increase in metabolic activity occurred in animals with chemical evidence of hepatocellular injury and histologic evidence of hepatocyte necrosis. During endotoxemia the liver becomes the major organ of glutamine consumption. This accelerated utilization provides carbons for energy and gluconeogenesis, nitrogen for ureagenesis, and substrate for nucleotide and glutathione biosynthesis in order to support cell repair and detoxification reactions.