Recently, it has been demonstrated that free PSA/total PSA ratio in prostate cancer patients is lower than patients with benign prostatic hyperplasia and the percentage of free PSA improves specificity and sensitivity of prostate cancer diagnosis (Catalona et al, 1995; Törnblom et al, 1999; Veltri and Miller, 1999). Here, KLK3 is linked to prostate carcinoma.