Prostate cancer is notoriously difficult to treat, which makes its early detection a priority. Biomarkers have been used to diagnose and monitor prostate cancer for more than 50 years, and the discovery of the serum marker prostate-specific antigen (PSA) significantly altered the detection and management of prostate cancer. But imperfect correlation with cancer hinders the usefulness of PSA. The elucidation and validation of new biological markers of prostate cancer should aid detection, and improve the application of the available therapeutics.