Recently, 12 new transductions of c-erbB have been identified in a series of Rous-associated virus type 1-induced erythroleukemias. During the passage of these new transducing viruses it has become apparent that the erythroleukemia in chicken 5005 contained two different c-erbB transducing viruses. One induces erythroblastosis, whereas the second induces angiosarcoma. The angiosarcoma- and erythroblastosis-inducing viruses appear to have had a common ancestor, since tumors induced by each contain a novel, 4.3-kilobase c-erbB-related EcoRI fragment. The angiosarcoma-inducing virus has been named avian angiosarcoma virus and is designated for the chicken in which it originated.