Background and Aims: Neopterin is a proinflammatory indicator thatplays a role in cell-mediated immunity, and elevated concentrations ofneopterin indicate the presence of interferon-γ in body fluids. In thisstudy, neopterin concentrations were determined in patients with avirus-induced chronic liver disease (chronic hepatitis, liver cirrhosis,and hepatocellular cancer), inactive hepatitis B virus carriers, and ina healthy control group to assess whether neopterin can be used asa disease marker in patients with virus-induced chronic liver disease.Materials and Methods: A total of 110 subjects (42 females and 68males, with an average age of 44±8.90 years) were included in thisstudy. Of these patients, 33 had chronic hepatitis; 22, liver cirrhosis;22, hepatoma; 18, inactive hepatitis B virus carriers; and 15 were includedin the healthy control group. Neopterin levels were measuredbefore and after interferon treatment in patients with chronic hepatitis.Data collected among the groups were analyzed statistically using theMann-Whitney test, considering p < 0.05 as statistically significant. Results:Neopterin concentrations and gender showed no statistically significantcorrelation. Patients with cirrhosis, hepatocellular cancer, andchronic hepatitis had statistically significantly higher neopterin levelsthan the healthy control and healthy carrier groups. A positive correlationwas observed between neopterin levels and other disease activityindicators such as aspartate transaminase, alanine transaminase, hepatitisB virus deoxyribonucleic acid, hepatitis C virus ribonucleic acid,erythrocyte sedimentation rate, and C-reactive protein levels, and theirlevels were also high. Although 14 patients, who were also evaluatedafter interferon treatment, showed good response to the treatment,no statistically significant correlation was observed between their neopterinlevels and disease activity indicator levels. Conclusion: Neopterinconcentrations were found to be significantly higher in patientswith inflammation than in inactive hepatitis B virus carriers who hadno ongoing inflammatory activity and in the healthy control group.No correlation was detected between neopterin levels and hepatitisB virus deoxyribonucleic acid and hepatitis C virus ribonucleic acid levelsin patients who received interferon treatment and benefitted fromit. Although neopterin levels indicate inflammatory activity in cases ofchronic hepatitis, liver cirrhosis, and hepatocellular cancer, additionalstudies are necessary to determine its usefulness in clinical practice.