In this project, we aim to analyze patients' gene expression profiling during the treatment. The current study will focus on 30 PEG-IFN and ribavirin treated patients with HCV genotype 1 infection. After the responding status of those patients has been confirmed, we will compare gene expression profiling among the different responses before and during treatment. By using this information, we can properly select the candidate genes, and establish a monitoring model with these biomarkers. This monitoring model can thus be applied to assess the efficacy of PEG-IFN plus ribavirin combination treatment.