Virion RNAs from the bovine enteric coronavirus and the human respiratory coronavirus OC43 were compared by one dimensional gel electrophoresis and by oligonucleotide fingerprinting. For each virus, approximately 55 per cent of the RNA migrated as a 6.8 Md species, 10 per cent as a 0.68 Md species, and 15 per cent as heterogeneous small molecular weight RNA. A sequence homology of greater than 96 per cent was observed between the 6.8 Md species from the two viruses. The 0.68 Md RNA is apparently an intravirion, subgenomic, polyadenylated molecule based on RNAse studies, oligo (dT)-cellulose chromatography, and hybridization to a cDNA clone of the 3' terminal 1.19 Kb region of the bovine coronavirus genome.