Identification of genes specifically expressed in adult and fetal testis is important in furthering our understanding of testis development and function. In this study,a novel human transcript, designated human testis cAMP-responsive element-binding protein (htCREB), was identified by hybridization of adult and fetal human testis cDNA probes with a human cDNA microarray containing 9216 clones.The htCREB transcript (GenBank Accession no. AY347527) was expressed at 2.35-fold higher levels in adult human testes than in fetal testes.Sequence and ntBLAST analyses against the human genome database indicated that htCREB was a novel splice variant of human CREB.RT-PCR-based tissue distribution experiments demonstrated that the htCREB transcript was highly expressed in adult human testis and in healthy sperm, but not in testes from patients with Sertoli cell-only syndrome. Taken together, these results suggest that the htCREB transcript is chiefly expressed in germ cells and is most likely involved in spermatogenesis.