BORIS, a paralogue of the transcription factor CTCF, is a member of the cancer-testis antigen family. BORIS is normally present only in the testis, however, it is aberrantly expressed in various tumours and, as recently reported, in leukocytes from breast cancer patients. The main aim of this study was to investigate BORIS expression in tissues and leukocytes from prostate cancer patients, and to correlate BORlS levels with clinical and pathological variables. To achieve this, BORIS immunoexpression was evaluated in human prostate tissues, cancer and benign prostate hyperplasia (BPH), and also in leukocytes from patients diagnosed with prostate cancer and BPH, and healthy donors. The staining was quantified using the immunoreactive score (IRS). BORIS, whilst absent in BPH tissues, was observed at varying levels in all prostate tumours analyzed, with the mean IRS= 6.78±0.89. Increased levels of BORIS protein positively correlated with Gleason score, T -stage and Androgen Receptor (AR) protein levels in prostate tumours. BORIS localization in the nucleus plus cytoplasm was also associated with higher BORIS levels and Gleason score. BORIS was not detected in leukocytes from healthy donors and patients with BPH, whereas 89% leukocyte specimens from prostate cancer patients were BORIS positive; the IRS values ranged between 1 and 8, with the average IRS= 2.51 ± 0.18. Positive relationship was observed between BORIS IRS, tumour stage and Gleason score however these results were not statistic all y significant. Detection of BORIS in prostate tumours suggests potential applications of BORIS as a biomarker for prostate cancer diagnosis, as an immunotherapy target and, potentially, a prognostic marker of more aggressive prostate cancer. The association of BORIS with AR indicates BORIS involvement in the growth and development of prostate tumours. Although BORIS has been shown to have properties as a blood biomarker, further validation will be required due to the lack of statistical significance.