The clinical use of measuring hepatic hepatitis C virus (HCV) RNA before and after therapy in patients with chronic hepatitis C has been assessed in a number of small clinical trials. Viral clearance from the liver may be a better marker of long-term response than eradication of serum HCV RNA. The aim of this study was to evaluate quantitative hepatic HCV-RNA measurements before and after antiviral therapy. Two thousand eighty-nine chronic hepatitis C patients were enrolled in 3 published clinical trials evaluating interferon alfa-2b alone or with ribavirin either as initial therapy or for interferon relapse. Hepatic HCV-RNA quantitation was performed with a modified reverse-transcription polymerase chain reaction (RT-PCR) before and 24 weeks after therapy in 951 and 1,316 patients, respectively. Pretherapy hepatic HCV-RNA concentrations correlated best with serum HCV-RNA concentrations (R =.236, P =.0001) and negatively correlated with alanine transaminase (ALT) values (-0.178, P =.0001), duration of infection (-0.09, P =.02), parenchymal injury (-0.135, P =.0001), histologic activity index (HAI) inflammatory score (-0.085, P =.01), Knodell fibrosis score (-0.072, P =.03), and body weight (-0.078, P =.02). In paired liver biopsy specimens (n = 534), change in hepatic HCV RNA correlated with the change in the HAI (R =.346, P =.0001). Of 400 sustained virologic responders (SVR), 393 (98%) had undetectable hepatic HCV RNA, whereas 7 (2%) had detectable hepatic HCV RNA; 5 have been followed and 2 have had reappearance of serum HCV RNA 12 months after therapy. In conclusion, measurement of hepatic HCV RNA before or after therapy reflects changes observed in serum HCV RNA, and correlates inversely with hepatic inflammation and fibrosis, but otherwise has minimal clinical use.