Two commonly used therapies on prostate cancer-radiation and total androgen blockade-induce predictable histologic changes in the tumor tissue. With the increasing use of posttreatment biopsies to evaluate patients receiving radiation therapy and the use of neoadjuvant total androgen blockade before radical prostatectomy, recognition of these alterations is of considerable importance to pathologists. Additionally, the significance of the observed changes, as regards evaluating the therapeutic response, is of considerable interest. The purpose of this report is to review the current knowledge of these important issues.