Eligibility Criteria:
Inclusion Criteria for Step 1:
* HIV infected
* Stable antiretroviral therapy for at least 8 weeks prior to study entry OR have not received any antiretroviral therapy for at least 4 weeks prior to entry
* HIV viral load less than 50,000 copies/ml within 6 weeks prior to study entry
* CD4 count greater than 200 cells/mm\^3 within 6 weeks prior to study entry
* Hepatitis C virus (HCV) infected
* Either HCV treatment naive OR previously treated with interferon (IFN), PEG-IFN, IFN and ribavirin, or PEG-IFN and ribavirin for at least 12 weeks and HCV RNA positive following their last course of HCV treatment
* Chronic liver disease consistent with chronic viral hepatitis
* At least stage I fibrosis on a liver biopsy obtained within 104 weeks of study entry
* If at stage VI fibrosis, Child-Pugh-Turcotte (CPT) score of 5 or less and no more than Child-Pugh Class A
* Liver enzyme (alanine aminotransferase \[ALT\], aspartate aminotransferase \[AST\], and alkaline phosphatase) levels 10 times or less than upper limit of normal
* Agree to use acceptable methods of contraception
Inclusion Criteria for Step 2:
* Currently enrolled in Step 1 or received 12 weeks of PEG-IFN plus ribavirin outside this study
* Detectable HCV viral load and \<2 log10 decrease from baseline in plasma/serum HCV viral load at Week 12.
* On Step 1 study treatment for no longer than 18 weeks
Inclusion Criteria for Step 3:
* Currently enrolled in Step 1
* Undetectable HCV RNA or a 2-log or greater decrease in plasma/serum HCV viral load.
* On Step 1 study treatment for no longer than 18 weeks
Exclusion Criteria for Steps 1 and 3:
* Have received HCV treatment within 4 weeks of study entry. Participants currently receiving treatment for HCV, if non-EVRs, were considered for direct entry into Step 2, without the run-in period in Step 1.
* Could not tolerate treatment with PEG-IFN, defined as missing 3 or more consecutive PEG-IFN doses during the first 12 weeks or a total of 5 doses prior to Step 3 entry. Participants who have missed doses of ribavirin will not be excluded from Step 3 entry.
* Use of granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) within 14 days prior to study entry
* Alpha feto protein level 400 ng/ml or greater within 24 weeks prior to study entry, or alpha feto protein level greater than 50 ng/ml and less than 400 ng/ml (unless computed tomography \[CT\] scan or magnetic resonance imaging \[MRI\] shows no evidence of hepatic tumor) within 24 weeks prior to study entry
* Decompensated liver disease, including presence or history of ascites, variceal bleeding, and brain or nervous system damage as a result of liver damage
* Other causes of significant liver disease, including hepatitis A or B, excess iron deposits in the liver (hemochromatosis), or homozygote alpha-1 antitrypsin deficiency
* Use of systemic corticosteroids, interferon gamma, TNF-alpha inhibitors, rifampin, rifabutin, pyrazinamide, isoniazid, ganciclovir, or hydroxyurea within 2 weeks prior to study entry
* Known allergy/sensitivity to PEG-IFN alfa-2a or ribavirin or their formulations
* History of uncontrolled seizure disorders
* Clinically active thyroid disease. Thyroid hormone replacement therapy is permitted, but thyroid-stimulating hormone (TSH) and free thyroxine index (FTI) must be in normal range.
* History of autoimmune processes, including Crohn's disease, ulcerative colitis, severe psoriasis, and rheumatoid arthritis, that may be made worse by interferon use
* Any systemic antineoplastic or immunomodulatory treatment or radiation within 24 weeks prior to study entry
* Malignancy
* Active coronary artery disease within 24 weeks prior to study entry
* Acute or active AIDS-defining opportunistic infections within 12 weeks of study entry
* Hemoglobin abnormalities (e.g., thalassemia) or any other cause of or tendency to break down red blood cells (hemolysis)
* History of major organ transplantation with an existing functional graft
* Active drug or alcohol use or dependence that, in the opinion of the investigator, would interfere with study adherence
* Uncontrolled or active depression or other psychiatric disorder, such as untreated Grade 3 psychiatric disorder, medically untreatable Grade 3 disorder, or any hospitalization within 52 weeks of study entry that, in the opinion of the investigator, may interfere with study requirements
* Other serious illness or chronic medical condition that, in the opinion of the investigator, may have prevented participant's completion of the study
* Pregnant or breastfeeding