In the light of contributions from the literature, the authors describe their experience with metabolic problems in patients who have had a hepatectomy. The initial post-operative phase is characterised by changes proportional to the amount of parenchymal loss, consisting of a reduction in gluconeogenesis and visceral protein synthesis, accentuation of muscle proteolysis, and a slowing down of detoxifying activity with the accumulation of catabolic substrates, such as aromatic amino acids, which cannot be metabolised. However, provided that the operated liver is not cirrhotic and that the vasculo-biliary part of the remaining segments is left intact, the regeneration of the remaining parenchyma is completed within a few days and metabolic haemostasis of glycoproteins appears to be almost completely restored within the first week. The changes in the amino acid profile and their molar ratio, though transient, confirm the benefits of nutritional support that includes selective amino acids in the initial post-operative phase.