Prostatic acid phosphatase is a glycoprotein which is synthesized by the prostate gland. The acid phosphatase is a membrane of a diverse group of isoenzymes which are capable of hydrolyzing phosphate esters in acid medium. Prostatic acid phosphatase test is clinically useful prognostic information for predicting recurrence in men who are undergoing radical prostatectomy for prostate cancer. PAP is very useful in predicting distant failure in higher-risk patients for whom high levels of local control are achieved with aggressive initial local treatment. PAP is also valuable for following the progression of disease response to men therapy being treated by androgen ablation. A re-evaluation of the potential contribution of the PAP test seems timely, as prostate cancer care becomes increasingly focused on identifying the minority of patients who would be benefited from aggressive systemic therapy.