BACKGROUND/AIMS: Enhanced replication of hepatitis C virus (HCV) is well described in the setting of moderate to severe immunosuppression. The aims of this retrospective study were to determine the incidence of enhanced HCV replication in hepatocellular carcinoma (HCC) patients undergoing transarterial chemolipiodolization (TACL) and to identify the factors associated with enhanced replication of HCV. The clinical pattern of enhanced HCV replication was compared with hepatitis B virus (HBV) reactivation during TACL. METHODS: This study enrolled 49 anti-HCV-seropositive patients who were diagnosed with HCC between January 2005 and December 2010 and who underwent TACL using epirubicin and/or cisplatin with consecutive HCV RNA copies checked. For comparison, 46 hepatitis B surface antigen1-positive patients with HCC who were treated with TACL were also enrolled. The frequency, associated factors, and clinical outcomes of enhanced HCV replication were analyzed and compared with those of HBV reactivation during TACL. RESULTS: Enhanced replication of HCV occurred in 13 (26.5%) of the 49 anti-HCV-seropositive patients during TACL. Of these 13 patients, 4 developed hepatitis, but none of the subjects developed decompensation due to the hepatitis. No significant clinical factors for enhanced HCV replication during TACL were found. Compared with HBV reactivation, the frequency of hepatitis attributed to enhanced HCV replication was significantly lower than that for HBV reactivation (8.2% vs. 23.9%, P=0.036). CONCLUSIONS: TACL can enhance HCV replication; however, the likelihood of hepatitis and decompensation stemming from enhanced HCV replication was lower than that for HBV reactivation in patients undergoing TACL.