The incidence of prostate cancer in men is very high worldwide, being the most commonly diagnosed cancer in the USA. It is the second most common cause of deaths of all types of cancers and the incidence and risk rate is much higher in developed world than underdeveloped regions. Also, aging enhances the risk of prostate cancer as it is very rare in men under the age of 40 while it is very frequent over age of 65. The digital rectal examination (DRE) and Prostate specific antigen (PSA) blood test are two important ways to diagnose prostate cancer. This book presents and discusses the possible role of PSA in prostate cancer.