Extrahepatic glucose release was evaluated during the anhepatic phase of liver transplantation in 14 recipients for localized hepatocarcinoma with mild or absent cirrhosis, who received a bolus of [6,6-²H₂]glucose and L-[3-¹³C]alanine or L-[1,2-¹³C₂]glutamine to measure glucose kinetics and to prove whether gluconeogenesis occurred from alanine and glutamine. Twelve were studied again 7 months thereafter with 7 healthy subjects. At the beginning of the anhepatic phase plasma glucose was increased and then declined by 15% per hour. The right kidney released glucose, with an arterial-venous gradient of -3.7 mg/dl. Arterial and portal glucose concentrations were similar. The glucose clearance was 25% reduced but glucose uptake was similar to the control groups. Glucose production was 9.5±0.9 µmol/kg/min, 30% less than in controls. Glucose became enriched with ¹³C from alanine and especially glutamine, proving the extrahepatic gluconeogenesis. The gluconeogenic precursors alanine, glutamine, lactate, pyruvate and glycerol, insulin and the counterregulatory hormones epinephrine, cortisol, growth hormone and glucagon were several-fold increased. Extrahepatic organs synthesize glucose at a rate similar to postabsorptive healthy subjects when the hepatic production is absent, and gluconeogenic precursors and counterregulatory hormones are markedly increased. The kidney is the main but probably not the unique source of the extrahepatic glucose production.