From October 1999 to July 2002, 821 newly diagnosed untreated prostate cancer patients at Schiffler Cancer Center at Wheeling Hospital in Wheeling, W. Va., who had pretreatment enzymatic prostatic acid phosphatase (PAP) determinations, were evaluated to determine if PAP could refine the subset of those requiring radiographic staging. PAP was obtained using a microparticle enzyme immunoassay (MEIA). A multivariate logistic regression model was constructed using pretreatment variables to determine whether PAP represented an independent predictor of positive bone and/or CT scans. A linear regression evaluated the predictive value of age, PSA, prostate volume, PAP and percent positive biopsies with the subsequent radiographic work-up. Enzymatic PAP proved useful in the clinical staging of newly diagnosed, untreated prostate cancer Using cutpoints of 15 ng/mL for PAP and 50 ng/mL for PSA, the negative predictive value for radiographically detected metastases was 99.8%.