To begin to examine the function in the mouse testis of genes containing the zinc finger motif, we have screened an adult mouse total testis cDNA library with probes to a conserved region of zinc fingers. We have isolated cDNAs for a new murine zinc finger encoding gene that has been designated Zfp-37. Northern blot hybridization analysis revealed Zfp-37 transcripts at high levels in the testis, the only adult tissue in which Zfp-37 expression was observed. Zfp-37 was also expressed at lower levels in the mid-gestation embryo and placenta. The major testicular transcripts are 2.3 and 2.6 kb. A 4.0 kb transcript was detected at lower levels in the testis as well as in embryo and placenta. Northern blot and in situ hybridization analysis revealed that expression of Zfp-37 was most abundant in germ cells which have completed meiosis and are undergoing the complex morphogenetic changes of spermiogenesis. The pattern of expression of Zfp-37 and the presence of the zinc finger domain suggest that Zfp-37 may have a role in regulating spermiogenesis.