In essence, replication-deficient (RD) adenovirus (Ad) vectors can be considered to function as an extremely efficient DNA transfection system capable of providing transgene expression in up to 100% of cells both in vitro or in vivo. As researchers continue to realize the full potential of this vector system, discover novel applications, and further develop and enhance systems, the use of this vector system has increased exponentially. The exploitation of Ad recombinants in HCV research is encouraged by demonstration that the virus will efficiently infect and express transgenes in hepatocytes and that following iv inoculation, transgene expression can readily be detected in hepatocytes in the liver (1 –5 ). A number of HCV proteins have now been expressed in Ad recombinants (6 –8 ) whereas these vectors have also been used to deliver antisense and ribozyme molecules as prototype HCV therapeutics (9 ).