In order to study effects of different total parenteral nutritional regimens on the recovery of liver function and on plasma amino acid pattern after major hepatectomy, twelve healthy mongrel dogs were submitted to 70% liver resection and randomly divided into three different groups: group I (control group) received only 10% glucose; group II received 10% glucose plus 8.5% Freamine; group III received 10% glucose plus 100% branched chain amino acid (BCAA) solution. Blood samples were analyzed for determining biochemical parameters, including plasma amino acid levels, before surgery and on 3rd and 7th postoperative day. The 'BCAA group', compared to other groups, showed higher values of plasma proteins (p less than 0.01) and prothrombin activity (p less than 0.05) on the 3rd postoperative day. The total concentration of plasma amino acids decreased after hepatectomy. Gluconeogenetic amino acids alanine and glutamine were markedly decreased in groups II and III, likely due to their increased consumption during gluconeogenesis. Aromatic amino acids were increased in all groups, due to the transient liver insufficiency. BCAA markedly increased in group III on 3rd postoperative day and returned to basal values on 7th postoperative day; possible explanations of such alterations are discussed. Our findings suggest that BCAA may represent a first choice substrate in the early phase after hepatectomy.