Prostate cancer (PCa) is a disease with high incidence and prevalence. It is the most common noncutaneous malignancy among men in the U.S. Discovery of prostate specific antigen (PSA) revolutionized screening of PCa which was largely dependent on detection of prostatic and phosphatase and digital rectal examination. This book reviews the use of PSA as a biomarker and the various aspects of the possible role of PSA in prostate cancer. Moreover, the N-glycan structures described in PSA are examined from different origins, such as prostate tumour cell lines, seminal plasma from healthy donors, serum from PCa and prostate BPH patients. This book also sheds light on the potential clinical utility of cell-free DNA for prostate cancer screening, diagnosis and prognosis and assesses the attributes of circulating DNA in its environment. Recent advances and clinical trials in immunotherapy for prostate cancer are highlighted, along with an emphasis on those that employ prostate specific antigen (PSA) as a target. Other chapters evaluate post prostatectomy PSA level and its association with prostate cancer relapse. PSA and signal transduction in Prostate Cancer and PSA in bone metastases and its connection to the immune system are examined as well.