The enhanced accumulation of hepatic progenitor cells (HPCs) is related to the risk of progression to hepatocellular carcinoma (HCC). Interferon (IFN) treatment reduces HCC risk in patients with chronic hepatitis C virus (HCV) infection. However, the underlying mechanisms remain unclear. The aim of this study was to examine the effects of IFN treatment on HPC activation in HCV patients. Immunohistochemical detection and computer-assisted quantitative image analyses of cytokeratin 7 (CK7) were performed to evaluate HPC activation in paired pre- and post-treatment liver biopsies from 18 HCV patients with sustained virological response (SVR) to IFN-based therapy and from 23 patients without SVR, as well as normal liver tissues obtained from surgical resection specimens of 10 patients. Pretreatment HCV livers showed increased CK7 immunoreactivity, compared with normal livers (HCV: median, 1.38%; normal: median, 0.69%, P=0.006). IFN treatment reduced hepatic CK7 immunoreactivity (median, 1.57% pre-IFN vs. 0.69% post-IFN, P=0.006) in SVR patients, but not in non-SVR patients. The development of HCC following IFN treatment was encountered in 3 non-SVR patients who showed high post-IFN treatment CK7 immunoreactivity (>4%). Successful IFN therapy can reverse enhanced HPC activation in HCV patients, which may contribute to the reduced risk of HCC development in these patients.