Tobacco necrosis virus (TNV) and its satellite virus (STNV) each contain a single-stranded RNA genome, of about 1.4 X 10(6) and 0.4 X 10(6) daltons, respectively, which is very active in stimulating amino acid incorporation in a wheat germ cell-free system. With STNV RNA the predominant incorporation product of 22,000 daltons coelectrophoreses with viral coat protein and crossreacts with antibody to viral coat protein. A similar result is obtained with TNV RNA, the only major translation product being a 30,000-dalton protein which corresponds to the coat protein by gel sizing, serological tests, and tryptic peptide analysis. Other products appearing in smaller amounts are about 63,000, 43,000, and 26,000 daltons and smaller. The possible nature of these products is discussed, as well as the unusual feature of a large, presumably multigenic, viral RNA yielding the coat protein as the predominant translation product in a eukaryotic system. Much less STNV RNA than TNV RNA produces maximal translation. Cotranslation of both RNAs in vitro indicates that STNV RNA has a translational advantage over TNV RNA. The fact that these RNAs lack 5'-terminal capping and 3'-terminal poly(A) is discussed.