Vaccine vectors based on recombinant viruses have great promise to play an important role in the development of an effective HIV-1 vaccine. Within the last 10 years a wide range of viruses have been investigated for their ability to express protein(s) from foreign pathogens and to induce specific immunological responses against these antigen(s) in vivo. Each viral vector has its own unique biological characteristics and thus far none of them has proven to be an ideal candidate as a vaccine vehicle for HIV-1. This review focuses on both replication competent and non-replication competent viral vectors as a potential HIV-1 vaccine. Other approaches for the development of an HIV-1 vaccine are reviewed elsewhere and are beyond the scope of this review.