: Insulin resistance is associated with nonresponse to hepatitis C virus (HCV) treatment. In this multicenter, single-arm pilot study, adult, HIV/HCV genotype 1-coinfected previous nonresponders to peginterferon/ribavirin (PegIFN/RBV) with homeostatic model assessment of insulin resistance >2.5 were treated with pioglitazone (PIO) for 24 weeks followed by PegIFN/RBV/PIO. Three of 19 subjects (15.8%) achieved undetectable HCV RNA at week 24 of PegIFN/RBV/PIO, which was not significantly different than the historical null rate of 10% (P = 0.29, lower limit of the exact 1-sided 90% confidence interval 5.9%). Over the 24 weeks of PIO monotherapy, alanine aminotransferase and aspartate aminotransferase declined significantly and correlated with improved metabolic parameters.