SRY (sex-determining region of the Y chromosome) has recently been identified as a key regulatory gene in mammalian sex determination. The open reading frame of this gene contains an 80-amino-acid motif, the SRY-box, which shares a high degree of homology with a DNA-binding domain found in the high-mobility-group (HMG) proteins HMG1 and HMG2. The SRY box motif is highly conserved in several sequence-specific DNA-binding proteins that are known to act as transcription factors. Here we describe the use of degenerate PCR primers to identify SRY-related sequences containing the SRY-box motif from the genomic DNA of a variety of species. The results of this study suggest that in a diverse array of species SRY-related genes may serve as transcription factors that regulate a variety of developmental pathways, including sex determination.