AIM: To correlate hypervascular power Doppler ultrasonography with the histo- logical evaluation of microvasculature in the prostate using trans-rectal ultrasound (TRUS)-guided needle biopsy. MATERIALS AND METHODS: Ninety-six patients with a lower urinary tract symptoms (LUTS) and prostate specific antigen (PSA) value more than 4 ng/ml were evaluated using power Doppler ultrasonography before biopsy. The vascularity of the peripheral zone was graded on a scale of PZ0 to PZ2. Core needle biopsies were immunostained with CD31(DAKO) and counting was performed manually on separate high power fields (HPF; £ 400) in areas containing the highest number of vessels. RESULTS: There was a significant correlation between the grading system used for power Doppler and the microvessel density (MVD; PZ0 28.61 ^ 8.97,PZ1 36.00 ^ 12.11&PZ2 64.008 ^ 15.86; p , 0:001). There was also a significant differ- ence in MVD between benign, malignant and tissue cores with atypia and prostatic intra-epithelial neoplasia (PIN; p , 0:001 and p , 0:018; respectively). There was a significant correlation between malignant tissue having a higher Gleason score and increased MVD ðp , 0:001Þ: Furthermore, cancer biopsies having a high flow PZ2 are nearly twice as likely (63.2%) to have a Gleason score of 7 or more when compared those having a Gleason score of less than 7 (36.8%). CONCLUSION: The grading system of assessing the power Doppler flow signals appears to be of value as an indicator of MVD. It also correlates with a higher Gleason score and this may reflect the clinical outcome in prostate cancer. It deserves further study and evaluation as a prognostic indicator. q 2004 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.