Background and objectives: The measurement of alpha-glutathione-S-transferase enzyme Is one of the most sensitive indicators of hepatocellular function. Variation in the glutathione-S-transferase PI gene clusters has been intensively investigated and polymorphism has been described. The aim of the study was to assess whether an association exists between glutathione-S-transferase P1 gene polymorphism and serum alpha-glutathione-S-transferase concentrations for the first postoperative day in patients who underwent anaesthesia with sevoflurane. Methods: In all, 54 unrelated patients were enrolled in this study. Anaesthesia was induced with thiopental and fentanyl. Vecuronium was used for neuromuscular relaxation before endotracheal intubation. Anaesthesia was maintained with sevoflurane in a gas mixture containing 50% nitrous oxide in oxygen. Peripheral venous blood samples to determine serum alpha-glutathione-S-transferase concentrations were collected before induction (T-1), at the end of anaesthesia (T-2) and at 24-h postoperatively (T-3). Enzyme-linked immunosorbent assay (ELISA) immunoassay was used to measure alpha-glutathione-S-transferase levels. Genomic DNA was isolated from serum samples using a genomic DNA purification kit. In order to detect the variants of glutathione-S-transferase P1, polymerase chain reaction - restriction fragment length polymorphism analysis was employed. Results: Early postoperative serum alpha-glutathione-S-transferase levels for all patients were significantly increased when compared with preanaesthetic and 24-h postoperatively (P < 0.05). Serum alpha-glutathione-S-transferase concentrations, in individuals with glutathione-S-transferase P1 Ile105Val genotypes (heterozygote gene), remained elevated at 24 h (P < 0.05), whereas levels in individuals with glutathione-S-transferase P1 Ile105Ile (wild gene) decreased (P > 0.05). Conclusions: Although alpha-glutathione-S-transferase levels were elevated in all patients after sevoflurane anaesthesia, levels remained high at 24 h in patients with glutathione-S-transferase P1 Ile105Val genotypes compared to controls.