ev 2 is one of seven recently described genetic loci of chickens which contain structural genes for endogenous virus. ev 2 is present exclusively in line 72 chickens, an inbred strain of white Leghorns which is homozygous for the capacity to produce Rous-associated virus type 0 (RAV-0), a subgroup E virus. This phenotype is known as V+ and has been assigned a genetic allele designated V-E7. The segregation of ev 2 was followed in a genetic cross in which the V-E7+ phenotype was also segregating. The progeny of the cross were analyzed for endogenous viral loci by cleavage of embryo DNA with restriction endonuclease SstI, electrophoretic separation of the resulting fragments, and identification of bands containing viral sequences by hybridization of the DNA to radiolabeled viral RNA. Four endogenous viral loci, ev 1, ev 2, ev 4, and ev 5, were identified in the progeny of the cross. One of the progeny contained no detectable endogenous viral sequences. ev 1, ev 4, and ev 5 were present in progeny of both the V-E7+ and V-E7- phenotypes. ev 2 was present exclusively in progeny of the V-E7+ phenotype, and all V-E7+ progeny contained ev 2. In addition, one of the V-E7+ progeny contained only ev 2. FRom these data, we conclude that ev 2 codes for RAV-0 virus produced by the cells of line 72 chickens.