Genomic and cDNA clones encoding the chicken ZF5 transcription factor were isolated and sequenced. Conceptual translation of the cDNAs indicates that chicken ZF5 has five zinc fingers at its C-terminal end and a POZ/BTB protein-interaction domain at its N-terminal end. These two functional domains are more than 99% identical in amino acid sequence between the chicken and mouse proteins, whereas the region separating the POZ/BTB and DNA binding domains is only 74% identical. The entire 458 amino acid open reading frame is contained within a single exon, except for the initiator methionine codon which alone is supplied from an upstream exon by mRNA splicing.