Abstract: This invention is directed toward recombinant attenuated canarypox virus expression vectors containing exogenous DNA segments encoding lentiviral gene products. A parental canarypox virus (Rentschler strain) was obtained and attenuated through more than 200 serial passages on chick embryo fibroblasts. A master viral seed was subjected to four successive plaque purifications under agar and one plaque clone was amplified through five additional passages after which the stock virus was used as the parental virus in in vitro recombination studies. This attenuated plaque purified canarypox isolate was designated ALVAC. A series of ALVAC recombinants were generated that are capable of expressing different HIV and SIV gene products including Gag, Pol, Env, and Nef. These recombinants provide useful reagents for the generation of viral-specific immune responses.