A cDNA species, corresponding to a gene with testis-specific expression (TSGA), was isolated from a testis cDNA library. The temporal and spatial expression of TSGA was studied by in situ hybridization as well as RNA filter hybridization. In tissue sections, the TSGA sequence was confined to cells within the seminiferous tubules. For filter hybridization, RNA was isolated from testis of prepubertal rats of different ages as well as from enriched populations of various germ cell types. It was found that TSGA is expressed only in male germ cells and that the steady-state level of TSGA transcripts reaches a maximum during the meiotic and the postmeiotic stages of germ cell development, suggesting a meiotic or postmeiotic function for the encoded protein. TSGA encodes a putative protein having 1,214 amino acids and contains a zinc finger, a structure that previously has been shown to mediate binding to nucleic acids.