Testis specific protein kinases are important because of their potential role in spermiogenesis, sperm maturation and sperm function. To continue our studies on the testis specific serine/threonine kinase (TSSK) family, we isolated a PCR fragment encoding a member of testis specific serine/threonine kinase3 (TSSK3) from Mus musculus testis RNA using reverse transcription polymerase chain reaction (RT-PCR) with oligonucleotides. The sequence length of the target gene was identified as 804 bp encoding a protein of 268 amino acids.