DNA transcripts were prepared from three related viruses of hamster and analyzed by interviral hybridization and by reaction with cellular DNA. A virus (G-HaLV), isolated from a dimethylbenzanthraceneinduced tumor cell in Graffi hamsters, contained nucleic acid sequences highly specific for hamster cell DNA and did not react with mouse cell DNA nor did its transcript show homology (<5%) with mouse or rat viral RNAs. The hamster-specific sarcoma virus, B-34, isolated by Bassin and coworkers from tumors induced by the Harvey strain of murine sarcoma virus, contained mouse-, hamster-, and possibly rat-specific sequences. B-34 transcripts were predominantly mouse-specific. GLOH(-), a lymphomagenic virus derived by dilution beyond the transforming endpoint of a hamster-specific sarcoma virus obtained from tumors induced by the Gross pseudotype of murine sarcoma virus, also contained hamster- and mouse-specific sequences. Only a portion of its hamster sequence (about 50%) was shared with B-34 and G-HaLV viruses. As expected, transcripts of GLOH(-) virus were reactive with mouse and hamster cellular DNA.