Using a hepatitis C virus (HCV) subgenomic RNA replicon system, drugs currently being used to treat other human diseases were examined for their antiviral activities against HCV. Several drugs including sodium stibogluconate, a compound used to treat leishmaniasis, were capable of suppressing replication of HCV replicon. The antiviral effect of sodium stibogluconate was subsequently verified using a cell line (293EBNA-Sip-L) previously proved to be permissive for HCV infection/replication. An ex vivo assay using fresh human liver slices established and a panel of human liver slices was obtained from biopsy samples of patients infected with HCV was used to examine the antiviral activity of this drug. A nearly complete suppression effect was achieved in four of six human liver slices at the drug concentration of 100 microg/ml, lower than what was required to treat leishmaniasis. A human trial is mandatory to understand its clinical value in treating chronic hepatitis C.