Human prostate-specific antigen (PSA) is clinically most useful diagnostic marker for prostate cancer. The PSA gene is partially regulated by androgen hormone via androgen receptor (AR). Several transcription factors including novel transcriptional regulator, age-dependent factor (ADF) bind to AR promoter and play role in the regulation of AR gene expression. Earlier, an androgen responsive enhancer (-5824 to -3738) has been identified in 5'-flanking region of PSA gene. Here, we demonstrate by competitive electrophoretic mobility shift assay that ADF binds to a 19 bp sequence in PSA gene (-4372 to -4390) located within this enhancer region. This suggests that ADF may play a role in the regulation of PSA gene expression.