Background: Transcription factors (TFs) play key roles in gene expression regulation, so do the transcription cofactors and chromatin remodeling factors.Identifying them are primary and crucial steps for illustrating their functions and understanding the transcriptional regulation.However, until now, there is no a comprehensive animal TF family list and a database characterizing all the TFs based on families for the sequenced animal genomes.The existing databases only focus on single or a few genomes, and the TF family classification and annotation for animals also could be improved to better serve the community.