Free Prostate Specific Antigen (Free PSA) is one of two forms of PSA occuring in human serum. The other is complexed or Total PSA. Free PSA is primarily ordered when a patient has a moderately elevated total PSA that does not appear to be caused by a non-cancer-related condition. The results give the doctor additional information about whether a patient is at an increased risk of having prostate cancer and help with the decision of whether to biopsy the prostate.