Even though solutions of high branched-chain amino acids (BCAAs) are known to be beneficial to patients with hepatic encephalopathy, data on the effects of BCAA on liver regeneration are limited. Two groups of young adult rats were utilized in this study: standard total parenteral nutrition solutions were administered to group SS (22.59% of BCAAs in total amino acids) and solutions high in BCAAs were given to group HS (34.44% of BCAAs). After 2 days of infusion, 70% partial hepatectomy was performed and the TPN infusions were continued for another 3 days. Liver regeneration was estimated and changes in serum amino acid patterns were determined 3 days after hepatectomy. Thymidine incorporation into liver DNA, in group HS was significantly higher than that in group SS (378±56 vs. 324±38, p=0.032). In group SS, the total concentration of BCAAs decreased (165.11±39.90mg/dL and 145.56±29.53mg/dL, p=0.014) over the experimental period, whereas that of aromatic amino acids (AAAs) increased (226.56±36.5mg/dL and 247.00±48.36mg/dL, p=0.104). However, group HS showed no changes in BCAA or AAA sums over the experimental period. After major hepatectomy, supplementation with high BCAAs helps not only to maintain a stable plasma BCAA/AAA ratio, but also promotes liver regeneration.