Abstract Purpose To investigate the biological functions of protein kinase C delta (PKC delta) in spermatogenesis. Materials and Methods We examined PKC delta transcript in mouse testis by means of in situ hybridization and Northern blotting. Results In testes of normal mice, signals of PKC delta gene expression were detected specifically at the spermatid stage. The PKC delta gene was weakly expressed in 8-week-old mice and highly expressed by 12 weeks. However, the expression was not detected in testes of germ cell-deficient W/W sup v mice even at 12 weeks. Conclusions Protein kinase C delta gene expression may be controlled by specific developmental processes and PKC delta may play a role in spermatogenesis.