This is a Phase 3b/4, prospective, open-label, randomized, multicenter study of peginterferon alfa-2b plus ribavirin in participants with chronic hepatitis C, genotype 1. The study consists of two parts: (1) a noninterventional arm (HOMA IR <= 2) and (2) an interventional arm (HOMA IR > 2), where HOMA IR is the insulin resistance index for the participants calculated by fasting insulin (uU/mL) x [fasting glucose (mmol/L)/22.5]. Participants in the noninterventional arm are treated according to the European labeling and response rates are evaluated at Month 1 (optional), 3, 6, 12, and follow up. Participants in the interventional arm are treated with PEG-Intron 1.5 ug/kg (subcutaneous) once weekly plus weight-based REBETOL 800-1400 mg (oral capsules) daily for a variable period depending on their response at Week 12: (1) HCV-RNA positive with < 2-log drop in viral load, treatment will be discontinued; (2) HCV-RNA positive with >= 2-log drop in viral load; participants will be randomized (1:1) to Group A (stop treatment at Week 48) or Group B (stop treatment at Week 72); and (3) HCV-RNA negative, treatment will be changed to be according to the European labeling and response rates will be evaluated at Month 6, 12, and follow up. All participants will go on with their treatment after Week 12 until the results of the HCV polymerase chain reaction (PCR) are available (maximum of 4 weeks).