The avian erythroblastosis virus, E26, an acute leukemia virus, contains a transforming gene composed of two cellular components, v-myb and v-ets. The v-ets related sequences of man and other mammals consist of two transcriptionally active genes, ets-1 and ets-2, located on separate chromosomes. By contrast, both of these genes are contiguous in birds, are located on the same chromosome, and are coordinately transcribed. The human ets-1 and ets-2 gene products were identified by means of antibodies directed against the ets-1 and ets-2 encoded products. A 51 kD protein has been identified as the ets-1 gene product, and a 56 kD protein as the ets-2 gene product. Cellular fractionation studies indicated that the ets-1 protein is located in the cytoplasm and the ets-2 protein is nuclear. By comparison, the chicken ets protein, which contains both the ets-1 and ets-2 domains, distributes equally between the cytoplasm and nucleus. The differential compartmentalization of the ets gene products and their non-coordinate expression suggest that these proteins have different biological functions.