PCA3 gene has been discovered in 1999 because of its differential expression between prostate cancer and nonneoplastic tissue. Several studies evaluated its value for prostate cancer diagnosis. These papers are consistent with significant statistical accuracy of measure of the urinary number of PCA3 copies (PCA3 test). While sensitivity is slightly weaker than that of seric PSA, specificity as well as positive and negative predictive values are quite better. PCA3 test seems therefore to be a good indicator of prostate biopsy results. As a commercial kit is available, large studies will be conducted to confirm these results, precise when to perform the test and evaluate the benefit/cost ratio. One of the aims is better selection of those patients who will really benefit from prostate biopsies.