Using an in silico (electronic database) subtraction, we identified a new member of the Ret Finger Protein-Like gene family, Rfpl4. Rfpl4 encodes a 287 amino acid putative E3 ubiquitin-protein ligase with a RING finger-like domain and a B30.2 motif. Reverse transcriptase polymerase chain reaction and Northern blot analyses reveal that Rfpl4 encodes a 1.7kb mRNA detectable exclusively in the gonads of adult mice. In situ hybridization localizes Rfpl4 transcripts within the ovary to oocytes of primary and later stage follicles and in the testis to elongating spermatids. The Rfpl4 gene comprises three exons and maps to mouse chromosome 7. We have identified the human ortholog, which maps to 19q13.4. These studies suggest that RFPL4 mediates protein degradation pathways important for gametogenesis or early embryonic development.