Several peripheral blood mononuclear cell (PBMC) defects have been linked with hepatitis C virus (HCV) infection, including alterations in cytokine secretion and increased cell death. This study was performed to investigate the expression levels of signal transducer and activator of transcription 1 interferon regulatory factor 1 (IRF-1), and caspase 3 in PBMCs of patients infected with HCV. IRF-1, and caspase 3 expression levels were compared in PBMCs from 19 untreated (naïve) HCV+ patients, 8 treated (sustained responder [SR]) HCV patients, and 20 HCV- healthy controls. Moreover, PBMCs from naïve HCV+ patients and SR-HCV patients were also evaluated for HCV RNA expression. The expression levels of and IRF-1 were significantly downregulated in PBMCs from naïve HCV+ patients (P Keywords: PBMC; hepatitis C virus; IRF-1; caspase-3.