['To investigate the independent association between the homeostasis model assessment of the insulin resistance (HOMA-IR) score and rapid virological response (RVR) and sustained virological response (SVR) in chronic hepatitis C (CHC).', 'Observational prospective cohort study of 412 CHC patients [59% males; mean age 45 years; genotype 1 (44%), 2 (32%), 3 (19%) and 4 (5%)] treated with pegylated interferon α plus ribavirin.', 'A HOMA-IR ≥2.0 was present in 49% and a metabolic syndrome in 4% of patients. By multivariate analysis, independent predictors of SVR were the lack of advanced fibrosis (≥F3) in genotype 1 and a lower body mass index in genotype 3 patients. In the subgroup of patients in whom HCV-RNA was evaluated at week 4 (n = 281), independent predictors of RVR were HCV-RNA <700,000 IU/ml, age <40 years and lower aspartate aminotransferase:alanine aminotransferase ratio in genotype 1 and baseline HOMA-IR ≤2 in genotype 3 patients. No predictive factor of RVR was identified among genotype 2 patients. RVR was the strongest predictor of SVR among genotype 1 or 3 patients.'] Is the homeostasis model assessment of the insulin resistance score predictive of a sustained virological response in chronic hepatitis C patients?