Objective To explore the clinical value of resistance index(RI)of prostatic capsular artery in predicting or screening of prostate cancer(PCa)by comparing prostatic capsular artery RI with the serum total prostatic specific antigen(TPSA),fPSA/tPSA ratio and prostatic specific antigen dernsity(PSAD).Methods RI of prostate capsular artery,serum TPSA,of fPSA/tPSA ratio and PSAD were measured with colour Doppler ultrasonography in this subset of 203 patients who had undergone transrectal ultrasound guided prostate puncture biopsy.The patients were divided into two groups [PCa and benign prostatic hyperplasia(BPH)group] for comparative study.Results Of them,the level of TPSA were between 4 and 10 ng/ml(grey area)in 34 cases,accounts for 16.75%of the total subjects.All the others were outside the grey area.ROC curve analysis showed that the area under the curve(AUC)of RI of the capsular artery was 0.77,which was close to 0.84 and 0.86 of TPSA and PSAD.It indicated a similar value in predicting or screening PCa; while the AUC of fPSA/tPSA ratio was only 0.49,which had little clinical value.The fPSA/tPSA ratio and the mean value of PSAD in the grey area had significant differences(t=2.78,3.94,P＜0.02)between the two groups.However,the fPSA/tPSA ratio had no statistical significance in the high value area outside the grey area(t=0.873,P ＞ 0.05).And the mean value of RI of prostatic capsular artery had significant differences between the two groups both in the grey area and in the high value area outside the grey area(t=4.56,5.10,P ＜ 0.001).Conclusions RI of prostatic capsular artery can be steadily used to predict or screen PCa.It is not affected by the gray area of TPSA and is of great value in clinical practice.