HIV-infected patients 18 years of age and older with chronic hepatitis C infection may be eligible for this study. Patients must have an HCV viral load greater than 2000 copies/mL and a CD4 count that is either more than 500 cells/mm3, or more than 350 cells/mm3 with an HIV viral load no greater than 40,000 particles/mL. Candidates will be screened for current or previous diseases, conditions or treatments that may exclude them from this study. Screening includes a medical history and physical examination, eye examination, blood and urine tests, chest X-ray, electrocardiogram (EKG), liver ultrasound, and, possibly, a liver biopsy, if a recent one is not available. The liver biopsy is optional and is done to determine the severity of liver disease. Patients will be sedated for this test. The skin in the area over the biopsy site is numbed with a local anesthetic, and a needle is inserted rapidly into and out of the liver to obtain a small tissue sample. Patients remain in the hospital overnight for monitoring. Women of childbearing age will have a pregnancy test.