The intracellular localization of the avian myeloblastosis virus (AMV) genome was studied. Nuclear and mitochondrial DNAs from myeloblasts were examined by hybridization with 32P labeled AMV-RNA of high molecular weight for the presence of virus specific DNA sequences. Nuclear DNA (nDNA) from myeloblasts specifically hybridized with viral RNA, whereas purified closed circular mitochondrial DNA (mtDNA) did not hybridize with viral RNA. It was therefore concluded that viral genome was present in nuclear DNA and not in mitochondrial DNA. Likewise, in normal chick cells, nDNA but not mtDNA hybridized with viral RNA.</p