Insulin resistance and diabetes are major disease modifiers in chronic hepatitis C, as they increase liver fibrogenesis and reduce the rate of response to antivirals. Regarding the latter, a previous study showed that a sustained virological response (SVR) occurred in about one third of patients with genotype 1 and insulin resistance (measured as homeostasis assessment of insulin resistance, HOMA-IR > 2) vs. two thirds of genotype 1 patients without insulin resistance. These findings were independently confirmed by other studies and extended to non-responders with genotypes 2, 3 and 4. Thus, we suggested that insulin resistance should be corrected in patients with chronic hepatitis C not responding to currently available antiviral treatment, in order to improve response to retreatment. The modalities of this intervention, however, have not been established. In addition, the optimal HOMA-IR score to be attained has not been identified. To assess this point, we planned a prospective, multicenter study to investigate the efficacy and safety of the insulin-sensitizer pioglitazone (ActosTM, Takeda Pharma AG, Lachen, Switzerland) 15 mg QD, added to the pegylated interferon-α2a (PEG-IFN-α2a) (PegasysTM, Roche Pharma Schweiz AG, Reinach, Switzerland) 180 μg QW/ribavirin (CopegusTM, Roche) 1000-1200 mg QD combination therapy in chronic hepatitis C patients who had previously failed to respond (i.e. had detectable serum HCV RNA after 12 weeks of therapy) to a pegylated interferon-α/ribavirin combination without the insulin-sensitizer. All patients had a baseline HOMA-IR score >2 as additional inclusion criterion, because this was the threshold discriminating responders from non-responders in previous works. Diabetic patients were excluded.