The beta CK2tes gene encodes a new variant of the tissue-specific regulatory beta-subunit of casein kinase 2 (CK2). The beta CK2tes open reading frame comprises nucleotide stretches encoding for the conservative polypeptide motifs characteristic for the CK2 beta-subunit including the Glu/Asp rich region responsible for regulation of CK2, C-terminal fragment responsible for binding to the catalytic alpha-subunit, and "zinc finger" motif. Unlike conserved sequences of CK2 beta-subunits in other organisms the beta CK2tes polypeptide has no autophosphorylation site or other putative phosphorylation sites. beta CK2tes is expressed only in testes, whereas beta CK2 expression is maximal at embryonic stages and is detected also in larvae. We suggest that beta CK2tes determines substrate specificity of CK2 and/or CK2 activity during spermatogenesis in Drosophila.