To assess the prevalence and significance of arteriovenous fistulae after prostate biopsy, we performed color Doppler ultrasonography immediately after 136 consecutive transrectal prostate needle biopsies. Pathologic results were correlated with color Doppler ultrasonographic findings. Arteriovenous fistulae developed after 17 biopsies (13%), all closed spontaneously within 18 minutes, and none were associated with unusual bleeding. Carcinoma was noted in 25 biopsy specimens (18%), 10 (40%) of which were followed by arteriovenous fistula. The correlation between malignancy and postbiopsy arteriovenous fistula was statistically significant (P < 0.0004), consistent with hypervascularity known to be present in many prostate cancers.