The susceptibility of Vero cells and derivative cell clones to hepatitis C virus (HCV) infection was assayed by qualitative and quantitative polymerase chain reaction (PCR)-based methods. Cell extracts from Vero cells inoculated with HCV were tested for the presence of both positive and negative strands of HCV RNA; in parallel, cell-free HCV genomes were assayed in culture supernatant fluids. Quantitation of genomic HCV RNA molecules in infected cells by competitive reverse transcription PCR (cRT-PCR) indicated that HCV replication was more efficient in a derivative clone (named clone 10) than in parental Vero cells or other clones under study. Analysis of HCV-binding to cell receptors, performed by cRT-PCR quantitation of viral particles adsorbed to the cell surface, demonstrated a 10-fold higher virus-binding level of clone 10 than that of parental Vero cells. The results shown here indicate that the Vero clone 10 may constitute an efficient model system for analysing early events in HCV infection as well as a source of virus for diagnostic and biotechnological applications.