Background: Propofol can inhibit lipid peroxidation in various experimental models in order to protect the cell against oxidative stress and increase the antioxidant capacity of plasma. The aim of this study was to determine the influence of gene polymorphisms CYP2C9 430C> T, CYP2B6 516G> T and UGT1A9 98T> C on the catalase activity in ninety children of different sexes and ages undergoing total intravenous anesthesia. Material and Method: Anesthesia was induced by a bolus dose of propofol from 2.5 to 3.5 mg/kg body weight, after which it was maintained by continuous infusion of propofol via an infusion syringe pump (3 - 15 mg/kg/h). Five blood samples were taken from each patient included in the study: before propofol administration to determine the presence of gene mutations in propofol degrading enzymes, 10 minutes after induction of anesthesia, immediately before the end of the propofol infusion, and 10 and 20 minutes after the end of the infusion. HPLC analytical technique was used to measure plasma propofol concentration. Genomic DNA was isolated from whole blood using the commercial QIAamp DNA Blood Mini kit. The presence of polymorphisms was analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Plasma catalase (CAT) activity was determined by spectrophotometric method. Results: The highest CAT values were measured immediately before the exclusion of continuous infusion of propofol, when there was a significant increase in activity relative to first sample (p <0.01), followed by a gradual decrease in concentration in each subsequent sample (Table 1). Compared to the examined polymorphisms, lower activity of CAT ten minutes after induction of anesthesia was found in carriers of GG genotype for CYP2B6 (Table 2), compared to the group of patients with GT and TT genotype (p <0.05). Discussion: The influence of gene polymorphisms on the expression of antioxidant activity of propofol requires further research. [ABSTRACT FROM AUTHOR]