The purpose of this study is to investigate the efficacy and safety of Pegasys® 180μg for subcutaneous (s.c.) injection in interferon (IFN)-treated or IFN-untreated chronic hepatitis C patients except for those infected with genotype 1b of hepatitis C virus (HCV) and a high viral load (≥ 100 KIU/mL).

In addition, this study will explore the efficacy and safety of Pegasys® 180μg for s.c. injection given at 2 different periods between 24 and 48 weeks in IFN-untreated chronic hepatitis C patients.

Inclusion Criteria:

• Quantitative serum HCV-RNA is positive except for high viral load of genotype 1b (≥ 100 KIU/mL)
• Observation of serum ALT elevation above upper limit of normal
• Chronic hepatitis is evaluated as the negative result (< 0) calculated by the method of "formula for discrimination between chronic hepatitis and liver cirrhosis."

Exclusion Criteria:

• Observation of white blood cells ≦ 3000/mm3; neutrophils ≦ 1500/mm3; platelets ≦ 90,000/mm3; or hemoglobin ≦ 10 g/dL.
• Observation of the following situations and disease: severe renal disease, hepatitis B co-infection, de-compensated liver disease, liver cirrhosis, hepatocellular carcinoma, poorly controlled psychiatric disease, seizure disorders, immunologically mediated disease, severe cardiac disease, poorly uncontrolled hypertension, poorly controlled diabetes, chronic pulmonary disease, retinopathy, malignant tumor, and organ transplant