Glucose turnover is increased during shock and in acute sepsis, but relatively little information is available concerning the regulation of carbohydrate metabolism during the hypermetabolic phase of sepsis. In these studies peritoneal sepsis was induced in rats, following chronic vascular catheterization, by intraperitoneal administration of a pooled fecal inoculum. The resultant peritonitis has been shown to produce a sustained hypermetabolic state during the first three days of infection. Glucose and lactate kinetics were studied using a constant infusion of radiolabeled tracers during the peak of the hypermetabolic phase (day 2). The septic animals exhibited a 42% increase in glucose turnover and a 63% increase in the metabolic clearance rate of glucose, as compared to time-matched control rats. Hepatic glycogenolysis could only contribute 1% to 2% to the increased rate of glucose appearance. A major portion of the elevated glucose turnover was accounted for by a 93% increase in glucose recycling, indicating an enhancement of gluconeogenesis from glucose-derived gluconeogenic precursors. The increased importance of lactate as a precursor for gluconeogenesis in sepsis was indicated by the elevated lactate turnover (34%) and the increased percentage of 14C-glucose derived from 14C-lactate. The insulin to glucagon ratio was decreased in the septic animals as a result of a reduction in the plasma insulin concentration (56%) and an increased glucagon concentration (67%). We conclude that during the hypermetabolic phase of sepsis, the increased peripheral glucose uptake generated more gluconeogenic precursors but did not appear to have a major direct contribution to the increased aerobic metabolism.