Conventional methods of staging prostate tumors are highly inaccurate. To improve clinical staging, prostate-specific antigen (PSA) levels (> 10 ng/mL), sonographic tumor volume (> 3 cc), maximum tumor diameter, length of capsular tumor abutment, and overall impression of capsular irregularity suggesting periprostatic tumor spread were assessed in 29 men prior to undergoing radical prostatectomy for clinically localized tumor. After surgery, 18 men had tumor confined to the prostate, while 11 men had histologic evidence of extracapsular disease. Analysis of the parameters measured showed these were the most helpful factors in predicting the presence of extracapsular disease. However, the positive and negative predictive values were only 70 to 90 percent. Therefore, the clinical usefulness of any one measurement alone in determining treatment for the individual patient is limited. However, combining these parameters yields an improved prediction of extracapsular disease. All 6 patients with PSA < 10 ng/mL, tumor volume < 3 cc, and no capsular irregularity on ultrasound had localized disease (neg. predictive value = 100%), while all 7 patients who had more than one of these parameters had extracapsular disease (pos. predictive value = 100%). Thus, using the factors in combination may provide more accurate staging and thereby help in counseling patients regarding therapy.