Ewing's sarcomas are characterized by recurrent chromosomal translocations expressing EWS-ETS fusion proteins, the most common of which is EWS-FLI.(1-5) EWS-FLI is an oncogenic transcription factor that regulates genes involved in tumorigenesis.(6,7) Because the Ewing's sarcoma cell of origin remains unknown, a variety of model systems have been developed to study EWS-FLI fusions,(8-14) and multiple microarray experiments describing potential EWS-FLI target genes have been reported.(8,10,11,13,15-21) Each model has potential benefits and drawbacks, but a large-scale comparison of these has not been reported