Protein synthesis and degradation in liver tissue were studied in rats following induction of septic peritonitis by ligation and puncture of the cecum. Protein synthesis was studied by determining the rate of leucine incorporation into protein in incubated liver slices. Protein degradation was measured in vitro as release of trichloroacetic acid soluble radioactivity from protein prelabelled with 14C-leucine and in vivo from decay of radioactivity in hepatic protein labelled with 14C-sodium bicarbonate. Measurements 24 hours after induction of septic peritonitis showed increase in liver weight and total hepatic protein content. Protein synthesis was higher in rats with septic peritonitis than in control rats 12 and 24 hours after cecal ligation and puncture. Protein degradation was unchanged. The results support the concept that net production of hepatic protein is increased in septic peritonitis, due to accelerated synthesis and unchanged degradation. Since other hepatocellular functions were previously reported to be depressed in the same experimental model, the present results indicate that hepatic protein synthesis has high priority during sepsis.