e detected the SIV DNA in genome extracted from 11 paraffin-embedd-ed lymph node samples of 3 SIV-infected and treated monkeys and 4SAIDS model monkeys before or after treatment by methods of PCR andnested PCR. The resnlts showed that 10 of 11 samples were positive byPCR and all were positive by nested PCR, only 3 of 11 correspondingperiod peripheral blood samples were positive by virus isolation method.In this study, the specificity of PCR prodnction was indentified by BamHIrestrictive digestion. Our experiments proved that the SIV DNA detectionfrom lymph node tissue reflected SIV infection status in monkeys morecorrectly than the virus isolation from the corresponding period peripher-al blood,and provided experimental basis for the evaluation of AIDS drugsand vaccines.