To establish an animal model for AIDS, 6 juvenile rhesus monkeys were infected intravenously with cell-free SIVagmTYO-1, 5, or 7. One animal was infected with SIV of known pathogenicity isolated from a sooty mangabey (SIVsmm). The 2 animals infected with TYO-1, 1 of 2 infected with TYO-7 and the 1 infected with SIVsmm seroconverted within 4-8 weeks after infection and infectious virus could be recovered 8-10 or 44 weeks after infection. Three of the 4 seroconverted monkeys developed a persistent lymphadenopathy 12 weeks after infection. Rhesus monkeys infected with SIVagm could serve as a model to study HIV infection and for vaccine trials.