Significance HIV is primarily a sexually transmitted disease but little is known about the transmission of viral variants during sexual contact. An understanding of the types of viruses transmitted by sex may make it possible to design vaccines to prevent the transmission of HIV. Objective In this study we used the rhesus macaque/SIV model to test the hypothesis that specific viral variants are efficiently transmitted by intravenous inoculation but not by vaginal inoculation . Results Five animals were inoculated intravenously with a high dose of SIVmac251. This is a virus stock with that consists of many variants. Five animals were inoculated intravaginally with the same stock. All the animals became infected and we are currrently assessing the natuire of the viral variants that infected the animals. We will compare the variants that infected the IV and IVAG inoculated animals to determine if the route of inoculation influences the type of viruses which infect rhesus macaques. Future Directions If specific SIV variants are responsible for infecting animals after vaginal inoculation, we will serially passage a virus stock by intravaginally inoculating rhesus macaques sequentially. Then we will produce a stock from the plasma of the last animal and use that for vaccine challenge studies. KEYWORDS viral variants, HIV mucosal transmission