The prostate cancer 3 (PCA3) gene was discovered in 1999, on the basis of differential expression between cancer and noncancerous prostate tissue. Including the first study published in 2003, 11 clinical studies have evaluated its utility for the diagnosis of prostate cancer by measuring the number of PCA3 RNA copies in urine enriched with prostate cells. Although the sensitivity of the PCA3 test was less than that of serum prostate-specific antigen (PSA), its specificity appeared to be much better, particularly in patients with a previous negative biopsy. Recent studies also have suggested that this test could be used to predict cancer prognosis.