The DNA-binding specificities of transcription factors can be used to computationally predict cis-regulatory modules (CRMs) that regulate gene expression. However, the absence of specificity data for the majority of transcription factors limits the widespread implementation of this approach. We have developed a bacterial one-hybrid system that provides a simple and rapid method to determine the DNA-binding specificity of a transcription factor. Using this technology, we successfully determined the DNA-binding specificity of seven previously characterized transcription factors and one novel transcription factor, the Drosophila melanogaster factor Odd-skipped. Regulatory targets of Odd-skipped were successfully predicted using this information, demonstrating that the data produced by the bacterial one-hybrid system are relevant to in vivo function.