Prostate Specific Antigen (PSA) is a single chain glycoprotein produced by epithelial cells of the prostate gland. PSA is useful in the management of patients with prostate cancer. The measurement of serum PSA has become the most accepted test to indicate men who are at risk of having prostate cancer and who should be examined by other tests. Using a cut-off of 4 ngml, 92% of men over 50 years of age with malignant prostatic tissues, 8% of healthy men and 28% of men with benign prostate hyperplasia (BPH) test positive for PSA. Three major forms of PSA exist in the serum: free PSA, bound PSA and complex PSA. Bound PSA is found in higher concentrations in patients with prostate cancer whereas, free PSA is detected in higher concentrations in patients with BPH. If the free PSA to Total PSA ratio is 25%, it is unlikely that the patient has prostate cancer whereas, if free PSA is 0.15 ngmlcc), very high PSA (10 ngml) or a free-to- Total PSA ratio of 16% warrants systemic biopsy.