A transcript encoding a rat homologue of DZIP1 (DAZ-interacting protein) was isolated from testis RNA. Like human DZIP1, it contains a C 2H2 zinc finger domain. A predicted mouse homologue of DZIP1 was found in the GenBank database. Genome analysis indicated that while DZIP1 and mouse Dzip1 contain 22 and 20 exons, respectively, the rat sequence was intronless, confirmed by PCR on genomic DNA. This rat Dzip1 sequence is homologous to mouse Dzip1 exons 1-6 and DZIP1 exons 5-9. As this rat sequence was shorter than DZIP1 it was designated rat Dzip1S. The rat genome also contained a further predicted homologue of DZIP1 displaying conserved linkage homology with mouse Dzip1 and DZIP1. This sequence, if expressed, is the true rat homologue of DZIP1, designated rat Dzip1. Rat Dzip1S mRNA was present in all tissues examined by qualitative RT-RCR, and in situ hybridization of rat testis confirmed that expression of rat Dzip1S mRNA was confined to the spermatogenic lineage, specifically premeiotic spermatogonia.