PSA stands for prostate-specific antigen. PSA is a protein produced only in the prostate in significant amounts. An elevated or rising PSA can be a warning sign of prostate cancer. While PSA testing is useful in the early detection of prostate cancer, it is still only a guide. For example, many patients with an elevated PSA do not have prostate cancer, and some patients with a normal PSA do have prostate cancer. The true clinical benefit of PSA testing is controversial. General guidelines for PSA testing include a yearly PSA and prostate examination starting at the age of 50. For African Americans and patients with a family history of prostate cancer, screening is sometimes recommended starting at the age of 40.