We have isolated a series of human testis poly(A) cDNA clones by cross-hybridization to SPGY1, a Y gene homologous to DAZ. Their sequence analysis revealed an identical nucleotide composition in different 'full-length' clones, suggesting that all were encoded by the same gene. We mapped this gene to the short arm of chromosome 3 and designated it SPGYLA (SPGY like autosomal). Comparison of the SPGYLA cDNA sequence with the cDNA sequences of DAZ and SPGY1 revealed two prominent differences. The tandem repetitive structure of 72 bp sequence units (DAZ repeats) is absent. SPGYLA contains only one 72 bp sequence unit. Downstream of it, a specific 130 bp sequence domain is present which is absent in DAZ and SPGY1 but present in the mouse gene Dazla and in the Drosophila gene boule. SPGYLA encodes an RNA binding protein expressed only in the human male gonad. The data presented give strong evidence that not DAZ but SPGYLA is the functional human homologue of Dazla and boule.