Purpose:To evaluate the value of transrectal color Doppler in benign prostatic hyperlasia (BPH) and prostate cancer. Method: 18 normal subjects, 53 BPH and 14 prostate cancer cases were studied by transrectal color Doppler flow image (CDFI).Results:CDFI reveals a marked increase in blood flow of BPH and prostate cancer. In BPH, the flow signals mostly occurrd in the inner or central gland, and it was symmetric without an obvious focus. In prostate cancer, it was depicted with obviously abnormal flow within and around the cancer lesion or hypoechoic nodule. But there were no statistically significant differences in the resistive indexes between BPH and prostate caner.Conclusion:Transrectal color Doppler scanning could delineate lesions that difficult to see at gray-scale scanning, which had a little additional value over gray-scale scanning alone in diagnosis of prostatic disease.