Cells infected by Rauscher leukemia virus synthesize virus-specific RNA which can be detected by hybridization to the single-stranded DNA copy of the viral RNA. Evidence is provided that virus-specific RNA is present in free and membrane-bound polyribosomes of these cells. The relative content of virus-specific RNA, as measured by hybridization, is 6-10 times less on free polyribosomes than on membrane-bound polyribosomes. The messenger RNA associated with both classes of polyribosomes was characterized by density gradient centrifugation. In addition to a major RNA species identified as 36S RNA, at least 2 minor components in the 14S and 21S region have also been found. There is a striking difference in the distribution of these RNA species between free and membrane-bound polyribosomes.