In this study, the serum levels of IL‐18 in patients with hepatitis B (949.12; 723.70–1160.28 pg/mL) and hepatitis C (776.99; 653.48–952.39 pg/mL) were both at a high level when compared to healthy controls, suggesting that high concentrations of IL‐18 can induce high concentrations of IFN‐γ, causing liver damage. This evidence concerns the gene IL18 and hepatitis C virus infection.